President Donald Trump stood firm Sunday on his demand for billions of dollars to fund a border wall with Mexico, claiming "tremendous" support inside his camp on the contentious issue which has forced a government shutdown now entering its third week.
"We have to build the wall," Trump told reporters as he left the White House for the Camp David presidential retreat. "It's about safety, it's about security for our country.
The US president warned once more that he may invoke emergency powers to get a wall built without congressional approval.
"I may declare a national emergency, dependent on what's going to happen over the next few days," he said.
One prominent House Democrat, Adam Schiff, immediately rejected the talk of a national emergency.
He noted that when former president Harry Truman used such language in an attempt to nationalise the steel industry and end a labour strike during the Korean War, he was rebuffed by the Supreme Court.
"So that's a nonstarter," Schiff said on CNN. He said Trump had painted himself into a corner and needs to "figure out how he unpaints himself from that corner."
An impasse with lawmakers over funding for the border wall — Trump is demanding $5.6 billion, while Senate Democrats have offered $1.3 billion — has partially shut down the federal government since December 22.
Trump said Friday that the standoff could last "months or even years."
The shutdown has left some 800,000 federal workers sent home or working without pay.
Large numbers of federal contractors are also losing pay in what is already one of the longest shutdowns in US history.
Talks aimed at ending the shutdown were to resume Sunday afternoon in Vice President Mike Pence's office, a day after a meeting involving him and representatives of Chuck Schumer and Nancy Pelosi, the top two Democrats in Congress, made little headway.
Trump indicated, however, that he was not expecting a weekend breakthrough, saying there would be "very serious talks come Monday, Tuesday, Wednesday."
Trump repeated his claim that many furloughed federal workers "agree 100 percent" with his demands, while asserting he also had "tremendous support within the Republican Party."
But Democrats, who now control the House of Representatives, seem in no mood to make concessions on a border wall Pelosi has described as an "immorality."
Pelosi said in an interview that aired Sunday if the president "doesn't care whether people's needs are met, or that public employees are paid or that we can have a legitimate discussion, then we have a problem."
Reflecting the depth of the divide, she added on CBS's "Sunday Morning" that Trump sometimes gave the impression that "he would like to not only close government, build a wall, but also abolish Congress, so the only voice that mattered was his own."
Trump's acting chief of staff Mick Mulvaney told CNN on Sunday that Democratic negotiators seemed to have come to the talks Saturday "to stall."
Both Democrats and Republicans have attempted to pin the blame the other side for the shutdown — a disruptive political ritual almost unique to the American system.
"This shutdown could end tomorrow and it could also go on for a long time," Trump said. "It really depends on the Democrats."
Trump's fellow Republicans control the US Senate but are short of the 60 votes needed to pass budget laws, so some Democratic support will be needed for any move to end the impasse.
Building a wall along the 2,000-mile (3,200-kilometer) US-Mexico border was a central plank in the 2016 election campaign of Trump, who has sought to equate immigrants with crime, drugs and gangs.
Mulvaney said he had concluded that Democrats "think they are winning this battle politically and they're vehement because they think the president is paying a price politically. That's unfortunate."
But a leading Democrat involved in the negotiations, Senator Dick Durbin, pushed back. "I can't say that we're close (to a solution)," he told CBS, "because the president's made it clear he doesn't care."
As the impact of the shutdown spreads — with reports that it may affect food subsidies for the poor and the tax refunds many people depend on each year — Trump insisted that Americans, even those directly affected, understood his stance.
"I can relate and I'm sure that the people that are on the receiving end will make adjustments -- they always do -- and people understand."
The shutdown has left transportation security agents and FBI employees, among many others, working without pay.
The popular Smithsonian museums, just blocks from the White House, have been forced to close, while national parks have seen trash pile up and bathrooms go uncleaned.