US Readying More Military Aid as Ukraine Appeals for SupportThe United States is expected to soon announce up to $750 million in additional security assistance to Ukraine as Ukrainian leader Volodymyr Zelenskyy appeals for more help to beat back Russian forces. A senior congressional aide told Reuters that while the final package is still under discussion, it is likely to include heavy ground artillery systems, including howitzers. A senior U.S. defense official said Ukrainian forces have received "a significant amount" of the 100 so-called switchblade drones, equipped with tank-busting warheads, promised as part of an earlier $300 million security assistance package. The remaining drones are expected to arrive in Ukraine in the next week or so, as are additional Javelin anti-tank missiles. U.S. President Joe Biden and British Prime Minister Boris Johnson on Tuesday "affirmed their commitment to continue providing security and humanitarian assistance to Ukraine in the face of ongoing atrocities by Russia," the White House said in a statement. Biden also escalated his rhetoric against Russia, accusing President Vladimir Putin of engineering a "genocide" in Ukraine. "Your family budget, your ability to fill up your tank, none of it should hinge on whether a dictator declares war and commits genocide half a world away," Biden said during a visit to the U.S. state of Iowa to promote a program to help lower gasoline prices. The U.S. president later defended his decision to label Russia’s actions as a genocide while talking to reporters before boarding Air Force One. "I called it genocide because it has become clearer and clearer that Putin is just trying to wipe out the idea of being able to be Ukrainian, and the evidence is mounting," Biden said. "We’ll let the lawyers decide internationally whether or not it qualifies, but it sure seems that way to me," he added. Biden has repeatedly criticized Putin, publicly calling him a "war criminal" and demanding that Putin stand trial after evidence of atrocities was discovered in Bucha, a suburb of the Ukrainian capital of Kyiv. "Calling things by their names is essential to stand up to evil,” Ukrainian President Volodymyr Zelenskyy tweeted late Tuesday. “We are grateful for U.S. assistance provided so far and we urgently need more heavy weapons to prevent further Russian atrocities." The Pentagon is holding a classified meeting Wednesday with the heads of the largest U.S. defense contractors to discuss meeting Ukraine’s needs for weapons. Deputy Defense Secretary Kathleen Hicks told reporters she will attend the talks. In Kyiv, Zelenskyy was due to host Polish President Andrzej Duda, Lithuanian President Gitanas Nauseda, Latvian President Egils Levits and Estonian President Alar Karis. "Our countries are showing support to Ukraine and President Zelenskiy in this way," Jakub Kumoch, a Duda adviser, tweeted Wednesday. For weeks, Western and Ukrainian officials have complained of mounting evidence of what they say are systematic atrocities and war crimes being committed by Russian forces retreating from parts of northern Ukraine. But if there was any hope Russia might bring its nearly month-and-a-half-long invasion of Ukraine to an end anytime soon, Putin brushed them aside Tuesday while speaking to workers at the Vostochny space launch facility in Russia’s Far East. The Russian leader said the fight would go on until the military achieved what he described as his country’s "noble" goals. Putin also vowed Russia’s military would proceed "rhythmically and calmly," blaming Ukraine for derailing peace talks. "We have again returned to a dead-end situation for us," Putin said of the negotiations, adding that Russia has no choice but to proceed. "I often hear questions about, is it possible to be quicker?" Putin told workers at the base, according to a Russian Ministry of Defense Telegram feed. "It is possible," he added. "It depends on the intensity of the hostilities." Chemical weapons allegations Putin’s comments on the war, his first in almost a week, follow allegations of new war crimes, including charges that Russian forces attempting to capture the besieged southern port city of Mariupol unleashed a chemical weapons attack. Russian officials have consistently denied the accusations, instead accusing the United States and Ukraine of preparing to unleash chemical and biological weapons. U.S. officials Tuesday said they are taking the latest allegations against Russia seriously but cautioned that confirming a chemical weapons attack could take time. "We cannot confirm the use of chemical agents at this time," a senior U.S. defense official told reporters, speaking on the condition of anonymity in order to discuss intelligence. "We’re still evaluating." "These are difficult things to prove, even when you are more proximate, and we are not," the official added. "We want to be very careful here before making a proclamation." Further complicating the situation, U.S. officials warned that several intelligence streams suggested Russia might try to mask a chemical weapons attack by mixing banned chemical agents with other substances. "We had credible information that Russian forces may use a variety of riot control agents, including tear gas, mixed with chemical agents," U.S. Secretary of State Antony Blinken said Tuesday. Battle for Mariupol Russian and Ukrainian troops are engaged in a pitched battle for control of the city. Ukrainian officials estimate as many as 22,000 people have died in Mariupol as a result of Russian airstrikes and shelling that have flattened much of the city. Despite social media posts from some Ukrainian and Ukrainian-backed forces that the country is running out of weapons, U.S. officials said Tuesday that Russia has not yet managed to take control. "Mariupol is still contested, and the Ukrainians are still fighting to defend (it)," Pentagon press secretary John Kirby told reporters Tuesday. "They haven’t given up on it, and we aren’t giving up on them, either." Western military officials have warned that Russian forces have increasingly targeted Mariupol with air and missile strikes as part of their concentrated effort to expand control in eastern Ukraine. "It is obvious that the Russians want Mariupol because of its strategic location," Kirby said. "It would provide them an unfettered and unhindered land access between the Donbas and Crimea." U.S. and British military have warned they expect fighting in the Donbas to intensify in the coming days and weeks as Russian forces pulled from around the Ukrainian capital of Kyiv and other northern areas resupply in Belarus and Russia and head east. Despite the onslaught, Ukrainian forces appear to have inflicted serious losses on the Russian military. U.S. estimates indicate Russia has lost about 20% of the combat power it arrayed against Ukraine since the invasion began February 24.