But Trump has vowed to veto the measure if it reaches his desk, and a veto override, which requires a two-thirds majority of both chambers, is seen as unlikely. Earlier on Tuesday, the house agreed by a vote of 229-193 to move to final debate and a vote passing the resolution. Republican Senator John Barrasso, a member of the Senate's leadership, told MSNBC in an interview that the legislation "may actually pass the Senate". Following a closed meeting of Republican senators and Vice President Mike Pence, Senate Majority Leader Mitch McConnell refused to predict the outcome, including whether senators ultimately could override a Trump veto. McConnell said Republican senators and Pence held a "robust, vigorous discussion" and that he had not "reached a total conclusion" over whether Trump's emergency proclamation was legal.

Meanwhile, the White House formally notified Congress, that when the measure passes Congress, Trump's advisers would recommend that he veto it in order to maintain the power he activated on February 15 as a way of circumventing Congress. Loading Trump argues he has the power to proclaim a national emergency to unilaterally direct existing money for building a border wall that Congress has refused to fully fund. "The current situation at the southern border presents a humanitarian and security crisis that threatens core national security interests and constitutes a national emergency," the White House statement warned. A Trump veto would be the first of his presidency and the first since Republicans lost majority control of the House in last November's elections.

Overriding such a veto in Congress would require two-thirds majorities in both chambers, making it highly unlikely, said lawmakers. "When you see the vote today, there will be nowhere near the votes to override a veto," US representative Steve Scalise, the No. 2 House Republican, said. The battle in Congress is the latest chapter in a long-running war between Trump and Democrats over border security, immigration policy and the "great, great wall" that Trump has pledged to build since becoming a presidential candidate. He originally promised that Mexico would pay for it, but after Mexico refused, he asked US taxpayers to foot the bill for a project Democrats say is unneeded and will not be effective. In his first two years in office, Trump's Republicans controlled both chambers of Congress, which under the US Constitution holds the national purse strings, but lawmakers failed to provide the full $5.7 billion in funding Trump wanted for his wall. Instead, Congress approved $1.37 billion for border barriers.

Angry over that decision, Trump declared an emergency and vowed to divert funds toward the wall from accounts already committed by Congress for other purposes. Loading That set up a test of the constitutional separation of powers between Congress and the presidency that will likely lead to a court challenge after lawmakers deal with the resolution. A coalition of 16 US states led by California has already sued Trump and top members of his administration to block his emergency declaration. Writing on Twitter on Monday, Trump, who says the wall is needed to stop illegal immigration and drugs, warned Republicans not to "fall into the Democrats 'trap' of Open Borders and Crime!"