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The following is a transcript of a joint call and webcast held by United States Steel Corporation and Nippon Steel Corporation on December 18, 2023.

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 1 of 12 , President & Chief Executive
Officer , Investor Relations Officer , Representative Director and Executive Vice President , GLJ Research , BofA Global
Research , KeyBanc Capital Markets , Exane BNP Paribas Operator Emily Chieng Acquisition of United States Steel Corp by
Nippon Steel Corp Company Participants David B. Burritt Emily Chieng Takahiro Mori Other Participants Gordon Johnson
Lawson Winder Phil Gibbs Tristan Gresser Presentation Good morning, everyone, and welcome to the United States SteelCorporation and Nippon Steel Corporation Joint Corporation call and webcast. As a reminder, today's call is being recorded. I'll
now hand the call over to Emily Chieng, Investor Relations Officer. {BIO 18699329 <GO>} Thank you, operator. Good
morning, everyone, and thank you for joining us on short notice today for U.S. Steel and Nippon Steel's joint conference call to
discuss the acquisition of U.S. Steel by Nippon Steel Corporation. Joining me on today's call is U.S. Steel's President andCEO, Dave Burritt; and Representative Director of NSC, Takahiro Mori. For Q&A, we will also have Senior Vice President
and CFO, Jessica Graziano; and Kevin Lewis, Vice President of Finance, joining. Please note that the slides we willreference today and the related press release are posted on the U.S. Steel Investor Relations page under the Overview
section. Before we start, let me remind you that information provided during this call may include forward-looking statementsthat are based on certain assumptions and are subject to a number of risks and uncertainties as described in our SEC
filings. Please review the

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 2 of 12 David B. Burritt cautionary
statements and other legal information starting on Slide 22 for further information. With that, I would now like to turn theconference call over to U.S. Steel CEO, Dave Burritt, who will begin on Slide 2. {BIO 5173302 <GO>} Thank you, Emily, andgood morning to all of you joining us. Today is an exciting day for U.S. Steel and for our industry by bringing together U.S.
Steel and Nippon Steel, we are enhancing competitive and innovative steelmaking in America. Today's announcement
follows the conclusion of a successful and very robust strategic alternatives review process conducted by our Board of
Directors. After thoroughly reviewing numerous alternatives, our Board unanimously approved the definitive merger
agreement that we announced earlier this morning, under which U.S. Steel will be acquired by and become a subsidiaryof NSC in a transaction valued at $55 per share, all cash. For our U.S. Steel stockholders, this announcement delivers
upon the commitment we made when we began the strategic alternatives review process to maximize value and toachieve a timely path to close through execution certainty. In meeting these goals, this transaction with NSC represents an
outcome that reflects the tremendous value we have created through our Best for All strategy. Moving to Slide 3, let's start withvalue. The $55 per share all cash merger consideration reflects significant value realization for U.S. Steel stockholders. The
consideration represents a premium of 40% compared to our closing price on December 15. The value created for U.S.
Steel stockholders through this transaction is a testament to the hard work and progress our employees have made as wedeliver our Best for All strategy, and I thank them for their continued focus on safety operating throughout the review process.
We've recently completed several strategic projects, whether it's the Gary Pig in 2022, the NGO electrical steel line justlast quarter, or the DR-grade pellet investment earlier this month, and we delivered them on time and on budget. This typeof consistent execution earned us credibility in the market. Everyone took notice, and it created a robust process withsignificant interest. Today's announcement is a direct result of the success to-date of the strategy, and we're not doneyet. In 2024, our biggest project to-date comes online, Big River 2, and you'll hear later the role Big River's continued
success played in igniting NSC's interest in U.S. Steel. The deal also comes with a high level of closing certainty. NSC has agreed
to honor all of the agreements between the U.S. Steel and the unions that represent U.S. Steel employees. The basic labor
agreements that were agreed to in September 2022 will remain in effect, and NSC is committed to maintaining these
relationships uninterrupted. This

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 3 of 12 expands upon NSC's existing strong
relationship with USW as they already have more than 600 USW represented employees in the United States. The
transaction also strengthens the existing competitive landscape in the United States Steel industry, underscoring ourconfidence in the receipt of the required regulatory approvals. We will continue to operate our mining and steel making
facilities in the U.S. for our U.S. based customers. And we do not expect any reduction in the U.S. Steel asset base to
close this transaction. We anticipate the deal will close in the second or third quarter of 2024. Upon closing, U.S. Steel will
operate as an indirect subsidiary of NSC and will remain headquartered in Pittsburgh, Pennsylvania. The iconic U.S. Steelbrand will live on. And that means the same high-quality steel service and reliability that U.S. Steel customers have cometo expect will continue. Let's turn to Slide 4. This transaction makes sense from several different angles and has a strong
strategic alignment, certainly from a financial uncertainty perspective, as I've just outlined, but also as we consider being
best, which is a theme that you have heard us discuss before, best in automotive steels, best in electrical steels, best inoperational excellence, best in decarbonization. Both of our companies are intensely customer focused, so we believe that thistransaction will allow us to be best at serving our customers. Through this transaction, we expect to enhance our productofferings with technical expertise drawn from NSC's global operations, their innovation, and their research and development.
The transaction will provide our customers with a truly global suite of automotive steel products. Automotive OEMs with a
global presence will have a global steel partner located in the United States to serve their needs, ranging from advanced highstrength steels to the high-end electrical steels the automotive industry is demanding. NSC's reputation precedes them as aleader in non-grain and grain-oriented electrical steels, and that technology is coming here for us to produce advanced, mind
melted, and Made in America electrical steels. In the U.S., we recently commissioned our non-grain-oriented electricalsteel line at Big River Steel in Arkansas. As part of the transaction, NSC will be acquiring the newest and most advanced
NGO asset in the United States today. Together with their global portfolio of electrical steels, we will be better able to serve
the electric vehicle and renewable energy revolution right here in the United States. We're also so enthusiastic about the sharedcommitment to research and development that will accelerate sustainable, profitable, and cutting-edge steel solutions for ourcustomers. In fiscal 2022, NSC invested approximately $500 million in research and development, and with this transaction,
intends to extend its investment now with increased R&D in the United States as well. Together, NSC and U.S. Steel will focus
on process technology research to innovate towards the most effective and environmentally sustainable processapplications.

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 4 of 12 Takahiro Mori Together, NSC and U.S.
Steel will also focus on product technology research to develop the next generation of steels for virtually any application.
Together, we are bringing greater innovation to the United States for the betterment of American workers, American
consumers, and American ingenuity. Our automotive customers are expected to soon have access to the world's best automotive
and electrical steel technology. And the best part? It will all be produced by an American workforce right here in the UnitedStates of America for our U.S. customers. So, to summarize, I couldn't be happier with the outcome of our strategic review
process, because it delivers on what is best for each of our stakeholders. And importantly, this is the best value with certainty
and timeliness to close. Now, as I mentioned at the start of the call, we're fortunate to have Takahiro Mori, Representative
Director of NSC, with us on the call to share NSC's perspective on the deal. Mori-san, the floor is yours. {BIO 22164358<GO>} Thank you, Dave, and good morning, everybody. This is Takahiro Mori, Representative Director of Nippon Steel. I'll starton Slide 5. On behalf of Nippon Steel, we want to express our excitement about our acquisition of U.S. Steel and extend
our welcome to the U.S. Steel employees. NSC has a deep respect for U.S. Steel, its history, and the contributions it has
made to society. This is a historic transaction for us. We believe we have found the right partner to accelerate our ambition as
the best steelmaker with world-leading capabilities, while also strongly aligning with U.S. Steel's Best for All strategy. We believe
this transaction is compelling for several reasons. First, we are combining our cutting-edge technologies to advanceinnovation and deliver high-grade steel products to address the growing global demand. We will share our leading
technologies and manufacturing capabilities to be at the forefront of innovation and digital transformation in steelmaking.
Next, both Nippon Steel and U.S. Steel have a shared commitment to drive the world's steel industry towards decarbonization.
Finally, NSC has a strong track record of positively working with all of our stakeholders, and we intend to continue thatapproach with U.S. Steel's employees, unions, customers, suppliers, and communities. Specifically, we will honor U.S. Steel's
commitment to its employees, including all collective bargaining agreements in place with its unions, and these relationships willcontinue uninterrupted. We look forward to building on U.S. Steel's strengths acrossFINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 5 of 12 several areas, including its strong
history, robust manufacturing base, excellent management team, dedicated employee base, and strong financial
position. I also want to highlight our commitments to maintain U.S. Steel's iconic name, brand, and headquarters in
Pittsburgh, Pennsylvania. And we believe that the mutual beneficial labor relations at U.S. Steel will continue to be based on
open dialogue between U.S. Steel and the unions representing its employees. Across the Board, the addition of U.S. Steelwill add significant human capital as well as manufacturing and R&D expertise supported by a strong balance sheet. For
those of you unfamiliar with Nippon Steel, let me give you a brief background. Headquartered in Tokyo, we are Japan's
largest steelmaker and one of the world's leading steel manufacturers. We are focused on expanding capacity in areas ofgrowing demand and in sectors in which our technology and the products are appreciated, especially in the United States.
With the addition of U.S. Steel's 20 million annual tons of capacity, we are significantly accelerating our path towards
achieving our ambitions. Post-scrolls, we are expected to have an approximately annual capacity of 85 million to 86 million tons.
This will accelerate our path towards our strategic goal of 100 million tons of annual global crude steel production. One of
the most exciting aspects of this transaction is our ability to combine our highly complementarily cutting-edge technologies tohelp advance innovation across the industry, as Dave has already highlighted. The benefits extend across both our
product technologies, where we will be better positioned to serve our customers as well as our operational and equipment
technology. That will allow us to operate more efficiently, while also supporting our sustainability goals. Finally, thecombined commitments to leveraging our disruptive R&D capabilities will remain steadfast. Synergies from a transaction will
be primarily driven by blending together advanced production technology and know-how between United States Steel andNippon Steel, including in cost-effective operations, energy saving, and recycling. On the Nippon Steel side, I want to highlight,
in particular, our strengths in innovation that result in increased production competitiveness. This strength is acrossseveral sectors, and for multiple different uses including electrical steel, sheet, and the flat product for automotive use,electrical and construction. Our aim is to deliver added value to customers through the application of NSC's producttechnologies. We are also excited to add U.S. Steel's state-of-the-art mini mills at the Big River site in Arkansas, which isone of the most advanced sustainable mills in North America. With Big River 2 scheduled to start production in 2024 and beat full production and capability level by 2026, nearly doubling current capacity, U.S. Steel is well

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 6 of 12 David B. Burritt positioned tocontinue to be a strong innovator. Big River Steel will have the ability to create differentiated automotive steel,sustainably produce electrical steels, as well as value-added products to the sub key steel industries. People may not knowthat Nippon Steel has successfully operated in the United States for almost 40 years because we have a relatively limited
footprint in the United States. Through the legacy of our U.S. subsidiaries, we are proud of the contributions they havemade to American industries. We first entered the United States when we established a joint venture with WheelingPittsburgh Steel in 1986, which later became a wholly-owned subsidiary. Our main products manufactured in the UnitedStates include forged rail steels and axles, coated flat steel, crankshafts for automotive, alloyed steel wire, and steel pipe.
Together with United States Steel, Nippon Steel is committed to serving customers in the United States seeking highperformance steel products to meet the needs of every application. The acquisition of United States Steel will significantly
build on the -- expand our operations in the country. Importantly, Nippon Steel and U.S. Steel have shared commitment todecarbonize by 2050. A key area of collaboration post-transaction will be continued to advance these efforts and globally on
alternative technologies in decarbonization. Nippon Steel is developing three breakthrough technologies towards carbon
neutrality, including hydrogen injection technology into blast furnaces, high-grade steel production in large-size electric arc
furnaces, and hydrogen use in the direct iron deduction process. U.S. Steel is similarly focused on reducing its carbon
footprint, including continuously striving to use less energy in its existing operations, integrating electrical arc furnace
capabilities into its footprint, and is constructing a second state-of-the-art mini mill in Arkansas. We believe that, together,
we can accelerate technological development and commercialization in decarbonization technologies to build towards amore sustainable society. With that, let me hand the call back to Dave. Thank you. {BIO 5173302 <GO>} Thanks, Mori-san. By
now, you're beginning to see the shared values and priorities of our two great companies. Turning to Slide 13, and before
we turn to Q&A, I want to highlight how this transaction also combines two like-minded steel companies. Despite being
headquartered on opposite corners of the globe, U.S. Steel and NSC share some important commonalities. The U.S. Steeland NSC combination is a natural one, built on a foundation of shared values and interests. We are both iconic companies inour respective countries, each with rich histories. We each have an unwavering commitment to safety and shared values, likeour steel principles.

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 7 of 12 Operator A - Emily Chieng Operator
Q - Tristan Gresser NSC and U.S. Steel are also aligned in our commitment to decarbonization by 2050. A key area ofcollaboration going forward will be to drive alternative technologies to focus on reducing the carbon intensity of thesteelmaking process. Finally, to all of the communities we have the privilege of serving, U.S. Steel will still be here for you in
Pittsburgh and in each of the locations we operate in. We are pleased that NSC is dedicated to being a productive
member of these communities and that the U.S. Steel relationships and longstanding tradition of charitable giving willcontinue. Before we move to Q&A, let me summarize the key messages from today's call. For U.S. Steel stockholders,the proposed deal represents maximum value, a timely transaction close, and a high level of closing certainty. For Nippon
Steel stockholders, today's proposed deal accelerates global ambitions while also strongly aligning with U.S. Steel's Best for All
strategy. Today's announcement joins two storied steel companies with shared values and visions for the future of steel.
Emily, let's open up the line for Q&A. Questions And Answers (Question And Answer) {BIO 18699329 <GO>} Thank you,
Dave. We ask that you each please limit yourselves to one question and a follow-up, so that everyone has the opportunity to
ask a question. Operator, could you please open up the line? Certainly. (Operator Instructions) One moment please for the firstquestion. And our first question is from the line of Tristan Gresser with Exane BNP Paribas. Please go ahead. {BIO 20323170<GO>} Yes. Hi, good morning, and thank you for taking my questions, and congratulations. The first question is for Dave. I
think when you look at the process and to create value, I believe you had to look at the completion risk and you
addressed that in the presentation and your remarks. So could you share a little bit you saw, how you view this deal fromthat perspective? And I'm not talking about antitrust, but more the political climate in the U.S. that could maybe be a bit
hostile to foreign ownership

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 8 of 12 A - David B. Burritt Q - Tristan
Gresser A - Takahiro Mori Q - Tristan Gresser A - Takahiro Mori Q - Tristan Gresser A - Takahiro Mori Operator even froma long time allied countries and notably in sector with national security aspect. That's my first question. {BIO 5173302 <GO>}
That's a really good question, Tristan. Thank you for answering [ph] that. I think the bottom line on all this is that the
combination is good for the United States and creates more competitive market here with one of the United States' greatest
allies. Just think about that for a minute. This is going to increase competition here in the United States with a great ally to
the United States. It's a great fit, and we do not see that as a high-level risk. In fact, we'd say low level of risk. {BIO 20323170<GO>} Okay. That's clear. My second question, if I may, for Takahiro Mori, please. I believe, given the decarbonization
targets you have in Japan and the push towards EAS technology there, and I think the introduction of carbon prices, whattypes of synergies or opportunities are you going to be able to leverage from a U.S. footprint in terms of the decarbonization
angle in Japan? And I'm talking, could we see some steel flowing from U.S. to Japan for certain uses? Or any color there thatyou could give would be appreciated. Thank you. {BIO 22164358 <GO>} Okay. As to the decarbonization, as I told you that
the Nippon Steel is challenging the three innovative technologies. So we can contribute to the United States Steel in thispoint. And also, in the United States that the CCS is very promising. So I think combining these two approaches -- different
approaches, we can contribute further for the decarbonization and sustainable society. {BIO 20323170 <GO>} All right. And
maybe just a quick follow-up to that. So there is no plan to, let's say, ship pig iron from the U.S. to Japan? {BIO 22164358<GO>} No, no. We don't have such plan at this moment. {BIO 20323170 <GO>} Okay. Thank you. {BIO 22164358 <GO>}
Yeah. Our next question is from the line of Lawson Winder with Bank of America Securities. Please go ahead.

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 9 of 12 Q - Lawson Winder A - David B.
Burritt Q - Lawson Winder A - Takahiro Mori Q - Lawson Winder Operator Q - Phil Gibbs A - Takahiro Mori {BIO
16002509 <GO>} Hello, everyone. Good morning. Good evening. Congratulations, and thank you for taking my questions.
First question would be, have there been any conversations with the UAW? And is there any implicit or explicit support fromthem? {BIO 5173302 <GO>} This is Dave. We've had outreaches at various levels in the organization, and I think the key
issue here that's really important is that this agreement honors and assumes all agreements between U.S. Steel and the
USW, and recognizes the union as the bargaining representative of the USW represented employees. There's nochanges to the existing collective bargaining agreements, but we have ongoing dialogues. I reached out this morning
to the Head of the Union, Dave McCall, I'm awaiting a call back. But I understand that at multiple levels throughout
the organization, we've made those connections. {BIO 16002509 <GO>} Fantastic. For my follow-up, Mori, if I could
please ask about the plans with Big River Steel 2. The concept with U.S. Steel was to offset the Big River Steel 2
production with closures elsewhere. Would that still be the plan under your ownership? Thank you. {BIO 22164358 <GO>}
We are supportive of the U.S. Steel plan for production in the future. So we're just following the current U.S. Steelproduction plan. And I think I believe that the U.S. Steel is planning to shift some quantity from the other mills to Big
River Steel 2. So I'm thinking or planning to follow that plan. {BIO 16002509 <GO>} Thank you all very much. Our nextquestion is from the line of Phil Gibbs with KeyBanc Capital Markets. Please go ahead. {BIO 17698714 <GO>} Hey, goodmorning. In terms of Nippon's existing automotive share in the United States or globally, is there any way to frame thatup? I'm trying to just think about the existing and future presence within that sector, given you highlighted it assomething that it's important. {BIO 22164358 <GO>}

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 10 of 12 Q - Phil Gibbs A - Takahiro Mori Q- Phil Gibbs A - Takahiro Mori Operator Q - Gordon Johnson A - David B. Burritt Q - Gordon Johnson A - David B.
Burritt Okay. So, I don't think we have a significant share in the United States automotive industry, but in Japan, we havea significant percentage of the share. I cannot disclose the share itself at this moment, but we are planning to inject
our technology to the United States Steel and to be more stronger or competitive to the automakers, and we would like toprovide high-quality steel and services that might improve the customer relationship in the United States. That's my plan. {BIO17698714 <GO>} That's helpful. Is there -- does this transaction at all change your plans in terms of finishing the EAF atCalvert with Arcelor? {BIO 22164358 <GO>} It doesn't affect our relationship with ArcelorMittal. The Calvert is Calvert, andthe U.S. Steel is U.S. Steel. {BIO 17698714 <GO>} Thank you. {BIO 22164358 <GO>} Yeah. (Operator Instructions) Our nextquestion is from the line of Gordon Johnson with GLJ Research. Please go ahead. {BIO 15743594 <GO>} Hey, guys.
Thanks, and congratulations on the deal. I think the price surprised me. So, I guess the first question is, this was kind of
asked initially, but just a quick follow-up. Given the extended authority of CFIUS in 2018, is there any risk you guys see ofthem coming in and potentially questioning this bill? And then a quick follow-up, please. {BIO 5173302 <GO>} I don't believe so,no. {BIO 15743594 <GO>} Okay. I'm sure that would be helpful. And then I guess a follow-up would be just the - - I guess,the utilization and the efficiency of the Big River. I guess, since acquiring Big River, the costs there have gone up slightly
since you guys still acquired them. Are there any specific plans you guys can highlight with respect to more efficiently
operate that asset? Thanks for the question. {BIO 5173302 <GO>}

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 11 of 12 Q - Gordon Johnson A - David B.
Burritt Q - Gordon Johnson A - David B. Burritt Operator Q - Tristan Gresser A - Takahiro Mori Gordon, I'm not sure I
understand you, but you're asking about what are we doing to improve the efficiency of Big River, was that thequestion? {BIO 15743594 <GO>} Yes, I guess more specifically, I just sent the query Big River in the first quarter of '21.
Just looking at the most recent filings, EBITDA per ton is down roughly 59% and the mini mill cost per ton are up
roughly 23%. So I guess the question is just going forward, what's the plan for all of this? {BIO 5173302 <GO>} Sure. We'realways focused on continuous improvement. I think the thing to really remember here is that the NGO galvanizing line, it's up
and running. We're going to get some benefits of that longer term. Obviously, there's startup and things like that that
we're going through with that process, but we feel absolutely wonderful about this Big River facility. And with Big
River too, it's going to be even more remarkable. So, I think this is a great asset for us and it continues to get better. We havestartups and we move forward, and we're pleased to report that we continue to be on budget, on time, and so this is awonderful place to be. {BIO 15743594 <GO>} Thanks, Dave. {BIO 5173302 <GO>} Thanks. Our next question is a follow-up
question from the line of Tristan Gresser with Exane BNP Paribas. Please go ahead. {BIO 20323170 <GO>} Yes, thank you fortaking the follow-up. This is a question for Takahiro Mori, please. I believe in your presentation there are mentions of theattractiveness of the U.S. steel market, but could you discuss a little bit Europe where you acquired three blast furnace in
Slovakia potentially? So what's -- what would be the strategy there? And a bit similar to Japan, there are a lot of pressure on
the blast furnace routes with decarbonization, so there could be some needed investment in that country. So how do you view
your presence in Europe? And what's -- what would be the strategy there? Thank you. {BIO 22164358 <GO>} Yeah. As to theEurope, this is quite new for us, and this is the price that we don't originally plan to get into -- the market we get into. So,after the transaction, we have

FINAL TRANSCRIPT 2023-12-18 United States Steel Corp (X US Equity) Page 12 of 12 Q - Tristan Gresser Operator A David B. Burritt Operator to think about how we can utilize the operation in the Europe. That's my current situation.
However, apparently in the United States, U.S. Steel has its plan at this moment and I have to dig in that plan. Is that good ornot? And after the evaluation of that plan, I'm going to start thinking what we can do in the future. {BIO 20323170 <GO>}
Okay. That's very clear. Thank you. And there are no further questions on the line at this time. I'll turn the call back to the
U.S. Steel CEO for closing remarks. {BIO 5173302 <GO>} Thank you to everyone for joining us this morning on such short noticeand for the discussion. As we conclude, a special thank you to our customers. Today's announcement highlights the close
partnership and the global innovation that we will bring to you. Importantly, thank you to our employees for your unwaveringcommitment to safety. And I'm so grateful for each and every one of you. We hope you're as excited about today's
announcement as we are. We look forward to updating you on the business' performance at our fourth quarter earnings
call and truly appreciate your interest in and engagement with U.S. Steel. U.S. Steel's best days are ahead together. Now, let's
get back to work safely. That does conclude the conference call for today. We thank you for your participation and ask that you
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Additional Information and Where to Find It This communication relates to the proposed transaction between the United States
Steel Corporation (the “Company”) and NSC. In connection with the proposed transaction, the Company will file relevantmaterials with the United States Securities and Exchange Commission (“SEC”), including the Company’s proxystatement on Schedule 14A (the “Proxy Statement”). The information in the preliminary Proxy Statement will not be complete
and may be changed. The definitive Proxy Statement will be delivered to stockholders of the Company. The Company may
also file other documents with the SEC regarding the proposed transaction. This communication is not a substitute for the
Proxy Statement or for any other document that may be filed with the SEC in connection with the proposed transaction. The
proposed transaction will be submitted to the Company’s stockholders for their consideration. BEFORE MAKING ANY VOTINGDECISION, THE COMPANY’S STOCKHOLDERS ARE URGED TO READ ALL RELEVANT DOCUMENTS FILED OR TO
BE FILED WITH THE SEC, INCLUDING THE PROXY STATEMENT, AS WELL AS ANY AMENDMENTS OR
SUPPLEMENTS TO THOSE DOCUMENTS, CAREFULLY AND IN THEIR ENTIRETY IF AND WHEN THEY BECOME
AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE COMPANY, NSC AND THE
PROPOSED TRANSACTION. The Company’s stockholders will be able to obtain free copies of the preliminary Proxy
Statement and the definitive Proxy Statement (in each case, if and when available), as well as other documents containing
important information about the Company, NSC and the proposed transaction once such documents are filed with the SEC,
without charge, at the SEC’s website (www.sec.gov). Copies of the Proxy Statement and the other documents filed with
the SEC by the Company can also be obtained, without charge, by directing a request to United States Steel Corporation,
600 Grant Street, Pittsburgh, Pennsylvania 15219, Attention: Corporate Secretary; telephone412-433-1121, or from theCompany’s website www.ussteel.com. Participants in the Solicitation NSC, the Company and their directors, and certain of
their executive officers and employees may be deemed to be participants in the solicitation of proxies from the Company’s
stockholders in respect of the proposed transaction. Information regarding the directors and executive officers of theCompany who may, under the rules of the SEC, be deemed participants in the solicitation of the Company’s stockholders inconnection with the proposed transaction, including a description of their direct or indirect interests, by security holdings orotherwise, will be set forth in the Proxy Statement when it is filed with the SEC. Information about these persons is
included in each company’s annual proxy statement and in other documents subsequently filed with the SEC, and will be
included in the Proxy Statement when filed. Free copies of the Proxy Statement and such other materials may be obtained
as described in the preceding paragraph. Forward-Looking Statements This communication contains information regarding
the Company and NSC that may constitute “forward-looking statements,” as that term is defined under the Private Securities
Litigation Reform Act of 1995 and other securities laws, that are subject to risks and uncertainties. We intend the forwardlooking statements to be covered by the safe harbor provisions for forward-looking statements in those sections. Generally,
we have identified such forward-looking statements by using the words “believe,”“expect,” “intend,” “estimate,” “anticipate,”“project,” “target,” “forecast,” “aim,” “should,” “plan,”“goal,” “future,” “will,” “may” and similar expressions or by using
future dates in connection with any discussion of, among other things, statements expressing general views about future
operating or financial results, operating or financial performance, trends, events or developments that we expect or anticipate will
occur in the future, anticipated cost savings, potential capital and operational cash

improvements and changes in the global economic environment, as well as statements regarding the proposed transaction,
including the timing of the completion of the transaction. However, the absence of these words or similar expressions does
not mean that a statement is not forward-looking. Forward-looking statements include all statements that are not historicalfacts, but instead represent only the Company’s beliefs regarding future goals, plans and expectations about our prospects
for the future and other events, many of which, by their nature, are inherently uncertain and outside of the Company’s or
NSC’s control. It is possible that the Company’s or NSC’s actual results and financial condition may differ, possibly
materially, from the anticipated results and financial condition indicated in these forward-looking statements. Management of
the Company or NSC, as applicable, believes that these forward-looking statements are reasonable as of the time made.
However, caution should be taken not to place undue reliance on any such forward-looking statements because suchstatements speak only as of the date when made. In addition, forward looking statements are subject to certain risks anduncertainties that could cause actual results to differ materially from the Company's or NSC’s historical experience and ourpresent expectations or projections. Risks and uncertainties include without limitation: the ability of the parties to consummate
the proposed transaction on a timely basis or at all; the timing, receipt and terms and conditions of any required
governmental and regulatory approvals of the proposed transaction that could cause the parties to terminate the definitive
agreement and plan of merger relating to the proposed transaction (the “Merger Agreement”); the occurrence of any event,change or other circumstances that could give rise to the termination of the Merger Agreement; the possibility that theCompany’s stockholders may not approve the proposed transaction; the risks and uncertainties related to securing thenecessary stockholder approval; the risk that the parties to the Merger Agreement may not be able to satisfy the conditions
to the proposed transaction in a timely manner or at all; risks related to disruption of management time from ongoing
business operations due to the proposed transaction; certain restrictions during the pendency of the proposed transactionthat may impact the Company’s ability to pursue certain business opportunities or strategic transactions; the risk that any
announcements relating to the proposed transaction could have adverse effects on the market price of the Company’s common
stock or NSC’s common stock or American Depositary Receipts; the risk of any unexpected costs or expenses resulting fromthe proposed transaction; the risk of any litigation relating to the proposed transaction; and the risk that the proposedtransaction and its announcement could have an adverse effect on the ability of the Company or NSC to retain customers
and retain and hire key personnel and maintain relationships with customers, suppliers, employees, stockholders andother business relationships and on its operating results and business generally; and the risk the pending proposedtransaction could distract management of the Company. The Company directs readers to its Form 10-K for the year
ended December 31, 2022 and Quarterly Report on Form 10-Q for the quarter ended September 30, 2023, and the otherdocuments it files with the SEC for other risks associated with the Company’s future performance. These documents containand identify important factors that could cause actual results to differ materially from those contained in the forward-looking
statements. Risks related to NSC’s forward-looking statements include, but are not limited to, changes in regional andglobal macroeconomic conditions, particularly in Japan, China and the United States; excess capacity and oversupply in thesteel industry; unfair trade and pricing practices in NSC’s regional markets; the possibility of low steel prices or excess ironore supply; the possibility of significant increases in market prices of essential raw materials; the possibility ofdepreciation of the value of the Japanese yen against the U.S. dollar and other major foreign currencies; the loss ofmarket share to substitute materials; NSC’s ability to reduce costs and improve operating efficiency; the possibility of notcompleting planned alliances, acquisitions or investments, or such alliances, acquisitions or investments not having the
anticipated results; natural disasters and accidents or unpredictable events which may disrupt NSC’s supply chain as well asother events that may negatively impact NSC’s business activities; risks relating to CO2 emissions and NSC’s challenge for carbon

neutrality; the economic, political, social and legal uncertainty of doing business in emerging economies; the possibility of
incurring expenses resulting from any defects in our products or incurring additional costs and reputational harm due to
product defects of other steel manufacturers; the possibility that we may be unable to protect our intellectual property rights
or face intellectual property infringement claims by third parties; changes in laws and regulations of countries where we
operate, including trade laws and tariffs, as well a tax, environmental, health and safety laws; and the possibility ofdamage to our reputation and business due to data breaches and data theft. All information in this communication is as of thedate above. Neither the Company nor NSC undertakes any duty to update any forward-looking statement to conform thestatement to actual results or changes in the Company’s or NSC’s expectations whether as a result of new information, future
events or otherwise, except as required by law.