WASHINGTON (Reuters) - U.S. President Donald Trump is expected to sign executive orders starting on Wednesday that include a temporary ban on most refugees and a suspension of visas for citizens of Syria and six other Middle Eastern and African countries, say congressional aides and immigration experts briefed on the matter. 
 
 Trump, who tweeted that a “big day” was planned on national security on Wednesday, is expected to ban for several months the entry of refugees into the United States, except for religious minorities escaping persecution, until more aggressive vetting is in place. 
 
 Another order will block visas being issued to anyone from Syria, Iraq, Iran, Libya, Somalia, Sudan and Yemen, said the aides and experts, who asked not to be identified. 
 
 In his tweet late on Tuesday, Trump said: “Big day planned on NATIONAL SECURITY tomorrow. Among many other things, we will build the wall!” 
 
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 The border security measures probably include directing the construction of a border wall with Mexico and other actions to cut the number of illegal immigrants living in the United States. 
 
 The sources say the first of the orders will be signed on Wednesday. With Trump considering measures to tighten border security, he could turn his attention to the refugee issue later this week. 
 
 Stephen Legomsky, who was chief counsel at U.S. Citizenship and Immigration Services in the Obama administration, said the president had the authority to limit refugee admissions and the issuance of visas to specific countries if the administration determined it was in the public’s interest. 
 
 “From a legal standpoint, it would be exactly within his legal rights,” said Legomsky, a professor at Washington University School of Law in St. Louis. “But from a policy standpoint, it would be terrible idea because there is such an urgent humanitarian need right now for refugees.” 
 
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 The Republican president, who took office last Friday, was expected to sign the first of the orders at the Department of Homeland Security, whose responsibilities include immigration and border security. 
 
 On the campaign trail, Trump initially proposed a temporary ban on Muslims entering the United States, which he said would protect Americans from jihadist attacks. 
 
 Both Trump and his nominee for attorney general, Senator Jeff Sessions, have since said they would focus the restrictions on countries whose migrants could pose a threat, rather than a ban on those of a specific religion. 
 
 Many Trump supporters decried former President Barack Obama’s decision to increase the number of Syrian refugees admitted to the United States over fears that those fleeing the country’s civil war would carry out attacks. 
 
 LEGAL CHALLENGES POSSIBLE 
 
 Detractors could launch legal challenges if all the countries subject to the ban are Muslim-majority nations, said immigration expert Hiroshi Motomura at UCLA School of Law. 
 
 Legal arguments could claim the executive orders discriminate against a particular religion, which would be unconstitutional, he said. 
 
 “His comments during the campaign and a number of people on his team focused very much on religion as the target,” Motomura said. 
 
 To block entry from the designated countries, Trump is likely to tell the State Department to stop issuing visas to people from those nations, according to sources familiar with the visa process. He could also instruct U.S. Customs and Border Protection to stop any current visa holders from those countries from entering the United States. 
 
 White House spokesman Sean Spicer said on Tuesday the State and Homeland Security Departments would work on the vetting process once Trump’s nominee to head the State Department, Rex Tillerson, is installed. 
 
 Other measures may include directing all agencies to finish work on a biometric identification system for non-citizens entering and exiting the United States and a crackdown on immigrants fraudulently receiving government benefits, according to the congressional aides and immigration experts. 
 
 To restrict illegal immigration, Trump has promised to build a wall on the U.S.-Mexico border and to deport illegal migrants living inside the United States. 
 
 Trump is also expected to take part in a ceremony installing his new secretary of homeland security, retired Marine General John Kelly, on Wednesday. 
 
 AUSTRALIA DEAL UNDER THREAT 
 
 Trump’s executive order threatens a refugee resettlement deal with Australia signed late last year, and could leave more than 1,000 asylum seekers in limbo. 
 
 The U.S. agreed to resettle an unspecified number of refugees being held in Papua New Guinea (PNG) and the tiny South Pacific island nation of Nauru on Australia’s behalf, under a deal to be administered by the U.N. refugee agency. 
 
 “Any substantial delay in the relocation of refugees...would be highly concerning from a humanitarian perspective,” Catherine Stubberfield, a spokeswoman of the U.N. High Commissioner for Refugees, told Reuters by email. 
 
 “These men, women and children can no longer afford to wait.” 
 
 The deal followed agreement by Australia in September to join a U.S.-led program to resettle refugees from Guatemala, Honduras and El Salvador as part of its annual intake. 
 
 Australia’s tough border security laws mandate that asylum seekers intercepted trying to reach the country by boat go for processing to detention camps on PNG’s Manus island and Nauru. 
 
 Australia does not provide information on the nationalities of those held, but around a third of the 1,161 detainees were from countries covered by the executive orders, lawyers and refugee workers for the asylum seekers told Reuters. 
 
 U.S. President Donald Trump speaks at the Armed Services Ball in Washington, U.S., January 20, 2017. REUTERS/Yuri Gripas 
 
 “We already didn’t have much hope the U.S. would accept us,” Behrouz Boochani, an Iranian refugee who has spent more than three years on Manus island, told Reuters. 
 
 “If they do not take us, Australia will have to.” 
 
 A spokeswoman for Australia’s Prime Minister Malcolm Turnbull declined to comment. ||||| President Trump plans to sign executive orders Wednesday enabling construction of his proposed wall on the U.S.-Mexico border and targeting cities where local leaders refuse to hand over illegal immigrants for deportation, according to White House officials familiar with the decisions. 
 
 The actions, part of a multi-day focus on immigration, are among an array of sweeping and immediate changes to the nation’s immigration system under consideration by the new president. The moves represent Trump’s first effort to deliver on perhaps the signature issue that drove his presidential campaign: his belief that illegal immigration is out of control and threatening the country’s safety and security. 
 
 Trump’s immigration blitz this week is widely seen inside the White House as a victory for the self-described populist wing of his inner circle — which includes chief strategist Stephen K. Bannon, attorney general nominee Jeff Sessions and top policy adviser Stephen Miller. 
 
 But discussions were ongoing Tuesday about just how far to go on some policies, in particular the Deferred Action for Childhood Arrivals program, known as DACA. The 2012 initiative has given temporary protection from deportation to hundreds of thousands of people who arrived in the United States as children. Trump vowed during the campaign to reverse it. 
 
 It was not yet clear late Tuesday whether DACA would be addressed as part of Trump’s immigration actions, according to a White House official, because of differing views among Trump’s advisers and associates about the timing, scope and political benefits of ending the program or suspending it for new entries. 
 
 “Many options are being worked through on DACA,” the official said. 
 
 Officials are considering, but have not decided yet, whether to indefinitely shut down the program that allows refugees from war-torn Syria into the United States. Trump may also put the entire refugee program for all countries on hold for four months, according to an administration official familiar with the options under discussion. 
 
 This official said that Trump will also potentially bar for 30 days the issuance of U.S. visas to people from Iraq, Iran, Libya, Somalia, Sudan, Syria and Yemen — all Muslim-majority countries — until new visa procedures are developed. Residents from many of these places are already rarely granted U.S. visas. Trump may ask DHS and the director of national intelligence to evaluate whether immigrants are being adequately screened for potential terrorist ties. 
 
 On Wednesday, Trump plans to speak to a town hall of employees at the Department of Homeland Security’s headquarters in Washington, where he is expected to sign the orders relating to the wall and “sanctuary cities.” The effort to crack down on these localities will resonate with the Republican base, which has long criticized local officials who refuse to cooperate with federal immigration authorities. 
 
 [What exactly are ‘sanctuary cities’ in immigration policy?] 
 
 Several people familiar with the discussions emphasized that the week’s actions are intended to start fulfilling Trump’s campaign promises on immigration and bring Republicans behind Trump on the issue, one day before he speaks at Thursday’s congressional GOP retreat in Philadelphia. These people spoke on the condition of anonymity because the executive orders were still being finalized. 
 
 White House aides said Trump planned to meet Wednesday with several parents of children who were killed by immigrants who are in the country illegally. These activists, who refer to themselves as “angel moms,” were frequently featured during Trump’s campaign rallies and during the Republican National Convention. 
 
 Any immigration measures announced by the president will set up a fierce battle in Trump’s first week between the White House and advocates for immigrants, who were reacting with alarm Tuesday as word spread that immigration was on the table. 
 
 The planned visit to DHS will be Trump’s second to a security agency since he took office Friday. He spoke to employees at the CIA’s headquarters in Northern Virginia on Saturday. 
 
 The presidential visit to DHS would symbolize some of the more controversial parts of Trump’s agenda. He centered his campaign to some degree on his proposal to build a wall along the U.S.-Mexico border to keep out illegal immigrants, a plan that has been vehemently opposed by Democrats and immigrant advocates. 
 
 Trump’s proposed wall is perhaps his most famous and disputed campaign proposal, and he feels so strongly about it that he told The Washington Post in an interview last year that building the structure “is easy. . . . It’s not even a difficult project if you know what you’re doing.’’ 
 
 [What it will take for President Trump to deport millions and build the wall] 
 
 Mexican President Enrique Peña Nieto will visit the United States next week to meet with Trump. The Mexican government has said it would not pay for Trump’s border wall despite Trump’s insistence that the country would provide funding at a later date. 
 
 House Republicans have said they plan to fund the barrier, which some experts have estimated will cost more than $20 billion. But experts say the wall would face numerous obstacles, such as environmental and engineering problems and fights with ranchers and others who would resist giving up their land. 
 
 Trump has also promised to beef up immigration enforcement along the border and inside the United States — notably by tripling the number of U.S. Immigration and Customs Enforcement agents — in an expensive and logistically difficult operation to remove millions of people from the country. 
 
 Perhaps most in dispute were Trump’s campaign comments on Muslims. He called at one point for a ban on all Muslims entering the United States as a counterterrorism measure and said he would halt immigration from Syria and deport Syrian refugees already in the country. 
 
 It is unclear how this week’s executive actions, orchestrated from the White House, will sit with the man who would enforce them: Homeland Security Secretary John F. Kelly. Kelly, a retired Marine general who was confirmed Friday, struck a markedly different tone from the president during his confirmation hearing, saying the controversial southwest border wall might not “be built anytime soon.’’ 
 
 Kelly noted that when he was a Marine officer in Iraq, his forces secured stability in part by reaching out to clerics and other Muslim leaders. He vowed to promote “tolerance” and said he didn’t think it was appropriate to target any group of people solely based on religion or ethnic background, including through the development of a registry. 
 
 DHS declined to comment Tuesday. But people familiar with the matter said Kelly, known for his blunt manner, is already under intense pressure from the White House to enforce the immigration crackdown on which Trump built his campaign. 
 
 Karen DeYoung, Ashley Parker and David Nakamura contributed to this report. ||||| WASHINGTON—President Donald Trump is set to announce plans to expedite construction of a wall along the Mexican border, and is preparing orders that ban people from countries deemed a terror risk from entering the U.S. as well as suspend the U.S. refugee program. 
 
 Mr. Trump plans to travel Wednesday to the Department of Homeland Security, where he said he would be announcing his border-security plans. He will also include an order aimed at punishing so-called sanctuary cities where law-enforcement officials limit cooperation...
– The clock is ticking on Donald Trump's first 100 days in office and he isn't dawdling over implementing the most controversial parts of his platform. The president plans what the Washington Post describes as an "immigration blitz" this week with executive orders on several areas of immigration policy. White House insiders tell the Post that Trump, who will speak about border security at the Department of Homeland Security’s headquarters on Wednesday, plans to start off with orders to begin construction of a border wall with Mexico and to punish "sanctuary cities" that fail to cooperate with federal immigration authorities. The Wall Street Journal's sources say Trump will also announce the hiring of more border agents. "Big day planned on NATIONAL SECURITY tomorrow," Trump tweeted late Tuesday. "Among many other things, we will build the wall!" Congressional aides tell Reuters that later in the week, Trump plans to issue executive orders temporarily banning almost all refugees and suspending visas for citizens of seven Muslim-majority countries: Iraq, Iran, Libya, Somalia, Sudan, Syria, and Yemen. The Journal's sources say Trump is considering shutting down the entire refugee program for as long as 120 days while he brings in measures including the "extreme vetting" he promised during his campaign. Insiders tell the Post that the Trump team is still debating policy in other areas, including President Obama's deferred deportation program.