White House adviser Stephen Miller said the Trump administration would do “whatever is necessary to build the border wall.” (Jabin Botsford/The Washington Post)

The White House and Democratic congressional leaders are at an impasse over negotiations to avoid a partial shutdown of the federal government at the end of the week, with both sides unwilling to budge from their positions on President Trump’s proposed border wall.

White House senior adviser Stephen Miller said Sunday that the administration would do “whatever is necessary to build the border wall,” including shutting down the government, even as polling suggests most Americans want Trump to compromise with Congress on the issue.

“This is a very fundamental issue,” said Miller, who has pushed to severely curtail immigration to the United States, on CBS’s “Face The Nation.” “At stake is the question of whether or not the United States remains a sovereign country.”

The White House has demanded $5 billion to partially pay for a wall along the Mexican border, a key campaign promise the Trump administration has yet to fulfill. Congressional Democrats have rejected that request, arguing the wall is wasteful and ineffective.

Congressional Republicans had been scrambling to find an alternative that would avoid a shutdown — such as a short-term funding measure to keep the government open for two or three more weeks. But the White House has signaled it wouldn’t support such a resolution, making it much more likely that spending for the government will lapse.

Even among Republican lawmakers, Trump’s wall proposal does not have universal support. When he said last week that he was willing to shut down part of the government over border security, some leading GOP lawmakers distanced themselves from his position.

Despite some backing for the wall among House Republicans, it was unclear whether Trump’s plan would even have enough votes to pass the GOP-controlled chamber.

And because of the 60-vote threshold in the Senate, the measure would be likely to fail there. Senate Republicans hold a 51-49 majority.

Lawmakers have until Dec. 21 to reach an agreement to avoid shutting down the government the next day, three days before Christmas. The consequences of a partial shutdown could ripple broadly across the U.S. economy, although economists caution that it would probably have to last more than a few days to drag on consumer spending.

“For businesses and consumers to cut back their spending, it would have to be an extended shutdown,” said Chris Rupkey, chief financial economist at MUFG. “We’ve seen this movie too many times.”

The shutdown could leave about a quarter of the government, as well as one-third of federal workers, without funding as the holidays approach. Federal agencies and senior officials are already beginning to prepare for that possibility.

Senate Democratic leaders signaled Sunday they were not budging from their negotiating position of providing $1.3 billion for border security — and they called on Trump to yield in his demands for $5 billion for the wall.

“President Trump should understand — there are not the votes for the wall, in the House or the Senate. He is not going to get the wall in any form,” Senate Minority Leader Charles E. Schumer (D-N.Y.) said on NBC’s “Meet The Press.”

Schumer added that Trump “shouldn’t use innocent workers as hostage for his temper tantrum to sort of throw a bone to his base.”

He urged Republicans to convince the president to back off his demands for wall funding.

Sen. Richard J. Durbin (D-Ill.), Schumer’s top deputy, emphasized the offer Democrats have made and urged Trump to agree to the $1.3 billion for more border security.

“It’s up to the president to accept this. I don’t think he will, but for the good of this country, I hope he does,” he said on ABC’s “This Week.”

A top GOP senator voiced hope that a shutdown could be averted — contrasting with the hard-line position Trump and Miller have taken. Sen. John Barrasso (R-Wyo.) said both short- and longer-term spending bills were possible but did not offer details of what a compromise that could please both sides should look like.

“There are people working on this to get to a conclusion so the government will remain open, which is what I believe the American people would prefer,” he said on “Face The Nation.”

Barrasso also emphasized that there are many means of securing the border that don’t amount to the kind of wall on which Trump has insisted.

“There are a lot of things you need to do with border security,” he said. “One is a physical barrier, but also the technology, the manpower, the enforcement, all of those things, and our current laws are in some ways an incentive for people to come to this country illegally, and they go through great risk and possibly great harm.”

Democrats will be in the House majority because of their wins in this year’s midterm elections, which could weaken the position of the White House in future government-funding negotiations.

An NPR/PBS NewsHour/Marist Poll released earlier this month found 57 percent of the country wants Trump to “compromise on the border wall to prevent gridlock,” while 36 percent say he should not compromise on the wall “even if it means a government shutdown.”

Last week, with television cameras rolling, Schumer and House Minority Leader Nancy Pelosi (D-Calif.) argued with Trump in a meeting in the Oval Office about the looming fight over the wall, which could spark the shutdown.

“I will take the mantle. I will be the one to shut it down. I’m not going to blame you for it. The last time you shut it down, it didn’t work,” Trump told the congressional Democrats. “I will take the mantle of shutting down, and I’m going to shut it down for border security.”