President Trump and White House officials pressed congressional Republicans on Sunday to use the looming threat of a government shutdown to win funding for a wall along the U.S.-Mexico border, a top priority for the administration as it nears the symbolic 100-day mark.

Trump wants funding to be included in a spending measure that would keep the government open past April 28, a determined effort that has prompted a possible standoff with lawmakers in both parties, who hope to avert a federal closure next weekend.

Trump’s push for fast action on his pledge to build the border wall is part of a mounting and, at times, tense scramble inside the administration to kick-start the president’s agenda, even if it risks dire political consequences. It follows weeks of frustration within the White House over inaction and stalemates on Capitol Hill over big-ticket items such as health care and tax cuts.

White House Chief of Staff Reince Priebus said in an interview Sunday with The Washington Post the president and his advisers remain “strong” in their commitment to securing funding for border security and a wall.

“This is what the president ran on,” Priebus said. “We want to get to a place this week where border-security money is being directed to the Department of Homeland Security so that we can begin surveillance and preliminary work, and then we will keep working on getting DHS what it needs for the structure.”

The timing promises a week of high drama on the Hill. The Senate returns Monday night, and the House returns Tuesday from a two-week recess, leaving just three days when both chambers will be in session to wrangle out a funding agreement. Negotiators worked throughout the break, but thus far a deal has not been struck.

The wall, which experts say would cost $21.6 billion and take 3½ years to construct, has emerged as a crucial sticking point for the White House, with the president insisting privately and publicly that progress toward its funding and eventual construction must be showcased this week.

President Trump wants funding for a Mexico border wall included in a bill needed to avoid a government shutdown

“Congress is right to be nervous, but that’s Trump’s style to be aggressive, ambitious, right out of ‘The Art of the Deal,'” said William Bennett, a conservative commentator and close friend of House Speaker Paul Ryan, R-Wis. “Everyone seems to be getting used to that and how Trump doesn’t want the half loaf but the whole loaf.”

In a tweet Sunday, Trump elbowed Democrats who have resisted his call to include wall funding. He chastised them for not wanting “money from the budget going to the border wall despite the fact that it will stop drugs” and gang activity, in his view.

Trump added he would continue to ask Mexico to pay for the project, another bold proclamation he made during the campaign. Meanwhile, he said, he will press Congress for funding “so we can get started early” on the “badly needed border wall.”

It remained unclear Sunday whether moderates within the GOP could convince the White House to avoid a shutdown. Democrats have insisted that they will not vote for any spending bill that gives the White House money or flexibility to begin construction of a border barrier. They believe the GOP will have to either abandon Trump’s demand or assume political responsibility for a shutdown.

“The burden to keep it open is on the Republicans,” House Minority Leader Nancy Pelosi, D-Calif., said Sunday on NBC’s “Meet the Press.” “Building a wall is not an answer. Not here or any place.”

Inside the White House on Sunday, West Wing aides made calls to congressional allies, while the president tweeted and reached out to several advisers, according to three officials.

Trump’s tweets included a shot at Democrats in which he drew parallels between border-wall funding and continued federal payments for subsidies under the Affordable Care Act. Some Trump associates said that they believe Democrats may be willing to deal on border funding if those payments are put on the table this week during cross-party talks.

“ObamaCare is in serious trouble. The Dems need big money to keep it going – otherwise it dies far sooner than anyone would have thought,” Trump tweeted.

The tweets did little to assuage concerns created earlier in the day when White House budget director Mick Mulvaney suggested Trump might not sign a spending bill that does not meet his demands.

“Will he sign a government funding bill that does not include funding for the border wall?” Chris Wallace, host of “Fox News Sunday,” asked Mulvaney during a televised interview.

“We don’t know yet,” Mulvaney responded.

Mulvaney said the White House expects Democrats to cave on the border wall in exchange for guaranteed payments under the ACA.

But Pelosi and Senate Minority Leader Charles Schumer, D-N.Y., have already rejected a White House offer to build into the spending bill a dollar-for-dollar match in wall funding and federal health-care payments. Negotiators want the stopgap measure to keep government open by keeping spending flat, including money to keep the ACA going. Trump is hoping to open that up for negotiation in exchange for wall money.