Updated at 2:40 p.m.: Revised to include fresh comment from President Donald Trump.

WASHINGTON — San Antonio Rep. Joaquin Castro on Friday filed a resolution aimed at stymieing the national emergency President Donald Trump declared to build more of his signature wall along the U.S.-Mexico border than Congress has funded.

The move puts the Texan at the forefront of Democrats' efforts to block the move.

"What the president is attempting is an unconstitutional power grab," Castro said. "This is an historic power grab, and it will require historic unity by members of Congress, Republican and Democrat ... to counteract the president's parasitic movement."

The "resolution of disapproval" is likely to pass the Democrat-run House, which is slated to take up the measure on Tuesday. Support from House Speaker Nancy Pelosi helped Castro, chairman of the Congressional Hispanic Caucus, line up more than 220 co-sponsors.

Rep. Joaquin Castro, D-San Antonio, on Friday filed a resolution designed to block the national emergency that President Donald Trump declared to build his border wall. (NICHOLAS KAMM / Agence France-Presse)

Its prospects are dicier in the GOP-run Senate, where many Republicans are reluctant to cross Trump despite their concerns about ceding even more power to the executive branch.

Trump last week raised the stakes by issuing the emergency declaration after Congress did not give him all of the $5.7 billion he wanted for a border wall. Such a barrier — a "big, beautiful wall" in Trump's parlance — was one of the president's central campaign promises, along with having Mexico pay for it.

His action would effectively bypass Congress, which controls the power of the purse under the Constitution.

The White House plans to use the declaration to free up about $6.6 billion, mostly by diverting funds from military construction efforts. The money would come on top of the $1.4 billion that Congress authorized for border fencing in a spending bill that Trump signed last week to avert another government shutdown.

"Everybody knows we need border security," Trump said Friday in an Oval Office appearance. "If we had a wall, it would be much easier. And frankly, it would be a job that would be perfecto. It would cost, actually, ultimately, a lot less money."

President Donald Trump has said he's going to "confront the national security crisis on our southern border." (Olivier Douliery / TNS)

Why this matters

Texas is front and center in the border wall battle.

Trump hosted a campaign rally last week in El Paso to make the case for a wall, drawing a counter-rally led by former Rep. Beto O'Rourke, a potential Democratic presidential contender. Any barriers constructed via Trump's declaration would be sure to wind, at least in part, through Texas.

Now a Texas Democrat is leading the fight to stop Trump's executive power play.

"This is obviously very consequential," Castro said, noting that a diversion of military construction funds could affect some bases in Texas.

Who's in and who's out

Castro had no trouble rallying support from Democrats, who see the wall as wasteful and the emergency as fake. But he has so far found only one GOP co-sponsor, Rep. Justin Amash of Michigan.

That tally doesn't necessarily reflect what the vote total will look like next week. Texas Republicans to watch include San Antonio Rep. Will Hurd, who has been a staunch opponent of Trump's wall, and Austin Rep. Roger Williams, who has expressed concern about the emergency declaration.

But many Texas conservatives are likely to back Trump, who has said that the emergency is all too real and that physical barriers are essential to securing America's southern border.

"Thankfully, we have a president who understands that it is vital that we take the appropriate action needed to secure this country with a border barrier," Rep. Louie Gohmert, R-Tyler, said last week.

Presidential candidate Julian Castro, former secretary of Housing and Urban Development, touted his twin brother's effort to block Trump's emergency declaration. (Charlie Neibergall / AP)

What Trump is saying

The president was quick to dismiss Castro's effort.

"Will I veto it? 100 percent," he said. "And I don't think it survives a veto. We have too many smart people that want border security."

Q: Will you definitively veto that resolution that's introduced today that would block the national emergency, if it passes?"



President Trump: "On the wall? Will I veto it? 100%." pic.twitter.com/KkQvx4ELsN — CSPAN (@cspan) February 22, 2019

How 2020 factors in

Castro's twin brother is Julian Castro, the former San Antonio mayor and Obama-era U.S. housing secretary. Julian Castro is now running for president, and he's sure to welcome any Castro buzz that might follow the effort to block Trump.

He said in Iowa on Thursday that his brother's legislation is "exactly what Congress should be doing."

"I'm happy that Speaker Pelosi is supporting Joaquin's legislation to stop this ridiculous declaration of a national emergency that is not really an emergency and the transfer of funds from worthy investment to something that the American people don't want, which is more fencing," he said.

What's next

If the House passes the resolution, the Senate then must vote on it within 18 days.

For Congress to override Trump's promised veto would require a two-thirds majority in both chambers. That could be tough sledding — particularly in the Senate, where the likes of Sen. John Cornyn have started giving Trump cover.

"It's shame that the president had to resort to his executive authority in order to do something Congress should've done," Cornyn said this week, per the Fort Worth Star-Telegram. "This was, to my view, an unnecessary step, in that Congress should've done its job."

If the pushback stalls in Congress, the dispute is sure to transition to the courts, where at least 18 states have filed a lawsuit to block the declaration on constitutional grounds.

Staff writer Todd J. Gillman contributed to this report.