The upper chamber is expected to vote on a resolution halting President Trump’s national emergency declaration to secure border wall funding.
The Senate is set to vote on the measure Thursday, which would force the president to use his first veto if it passes.
President Trump took to twitter saying he is prepared to use his veto if necessary, calling the southern border a “humanitarian nightmare.”
The measure is likely to pass with as many as five GOP lawmakers saying they will vote with Democrats.
Senator Susan Collins, Senator Mike Lee, Senator Lisa Murkowski, Senator Thom Tillis, and Senator Rand Paul have all said in advance they would vote for the measure.
A big National Emergency vote today by The United States Senate on Border Security & the Wall (which is already under major construction). I am prepared to veto, if necessary. The Southern Border is a National Security and Humanitarian Nightmare, but it can be easily fixed!
— Donald J. Trump (@realDonaldTrump) March 14, 2019
The Democrats would only need four Republicans to pass the resolution.
President Trump declared a national emergency last month in order to secure funding for border wall construction, which gives him access to $8 billion.