The Trump administration threatened to veto a resolution to block the president’s national emergency declaration to build a border wall between the U.S. and Mexico, which easily passed in the House of Representatives on Tuesday.

“The problem of large-scale unlawful migration through the Southern Border is enduring, and, despite the Administration’s use of existing statutory authorities, in recent years the situation has worsened in certain respects,” a statement from the White House reads.

“If H.J. Res. 46 were presented to the President in its current form, his advisors would recommend that he veto it.”

The vote, which passed the Democrat-controlled chamber 245-182, sets up a showdown over a president’s authority to bypass Congress for funding by invoking emergency powers. The measure now moves to the Republican-controlled Senate for a second vote in the coming weeks.

Thirteen Republicans broke ranks in the House and sided with the Democrats: Reps. Justin Amash of Michigan, Thomas Massie of Kentucky, Elise Stefanik of New York, Greg Walden of Oregon, Cathy McMorris Rodgers and Jamie Herrera Beutler of Washington, Will Hurd of Texas, Francis Rooney of Florida, Dusty Johnson of South Dakota, Fred Upton of Michigan, Brian Fitzpatrick of Pennsylvania, and Jim Sensenbrenner and Mike Gallagher of Wisconsin.

The Democrats need four Senate Republicans to vote with them to block the emergency declaration.

There are already three Republican senators on record against Trump’s emergency declaration: Susan Collins of Maine, Lisa Murkowski of Alaska and Thom Tillis of North Carolina, and there are reportedly “a handful” of other GOP senators leaning the Democrats’ way.

If the Senate votes in favor of the measure to block the president’s emergency declaration, Trump will issue a veto and the two chambers will vote again.

However, there’s little-to-no chance Congress will get the two-thirds majority in needed in each chamber to override a presidential veto.

The House’s vote is the first time Congress has formally attempted to block a presidential emergency declaration since the National Emergencies Act of 1976 was signed into law.

Democrats — and even some Republicans —  say the president is overstepping constitutional law and violating the separation of powers because Congress is the sole authority when it comes to appropriating federal funds.

Article I of the Constitution states: “No money shall be drawn from the Treasury, but in consequence of appropriations made by law.”

Democrats also have vowed legal challenges that would likely end up in the Supreme Court, where the outcome is far from certain.

Senate Majority Leader Mitch McConnell, R-Ky., said Tuesday, “I haven’t reached a total conclusion” yet on whether or not he thinks the emergency declaration is legal.

“We had a very fulsome discussion of this issue in the conference at noon today with the vice president,” McConnell added Tuesday. McConnell went to law school but he is not an expert on constitutional law.

Sen. Ted Cruz, R-Texas, is one of the senate’s foremost experts on constitutional law, and he said he is “still assessing the legal authority of the arguments that the administration is putting forward.”

“I emphatically agree that we have a crisis at the border and that we need to solve it, and I am grateful that the president and the administration are leading to secure the border and to build a wall,” Cruz said. “At the same time, I’ve long said that any president, Republican or Democrat, must follow the constitution and must follow the laws.

“So I’m taking the time to consider and analyze the specific statutory authorities the administration is relying upon and their arguments as to why they might apply.”

Democrats are of course confident in their estimation the emergency declaration is illegal.

“People will say, ‘Well, there have been a lot of emergency designations.’ That’s right,” House Majority Leader Steny Hoyer, D-Md, said. “This is the only one — the only one — that has been used to get around a Congress’s refusal to appropriate money for a particular objective.”