Millions of Americans are about to lose jobless benefits as President Donald Trump refuses to sign into law a $US2.3 ($A3.0) trillion pandemic aid and spending package, insisting it doesn't do enough for everyday people.
Trump stunned Republicans and Democrats alike when he said this week he was unhappy with the massive bill, which provides $US892 billion in badly needed coronavirus relief, including extending special unemployment benefits expiring on December 26, and $US1.4 trillion for normal government spending.
Without Trump's signature, about 14 million people could lose those extra benefits, according to Labor Department data.
A partial government shutdown will begin on Tuesday unless Congress can agree a stop-gap government funding bill before then.
After months of wrangling, Republicans and Democrats agreed to the package last weekend, with the support of the White House.
Trump, who hands over power to president-elect Joe Biden on January 20, did not object to terms of the deal before Congress voted it through on Monday night.
But since then he has complained it gives too much money to special interests, cultural projects and foreign aid, while its one-time $US600 stimulus checks to millions of struggling Americans were too small.
He has demanded that be raised to $US2000.
"I simply want to get our great people $2000, rather than the measly $600 that is now in the bill," the president tweeted on Saturday.
His refusal to sign prompted sharp rebuke from Biden, who called on the outgoing Republican president to act immediately.
"This abdication of responsibility has devastating consequences ...This bill is critical. It needs to be signed into law now," Biden, who is spending the holiday in his home state of Delaware, said in a statement.
Americans face an unprecedented holiday season amid a pandemic that has killed 330,000 people, with a daily death toll now repeatedly well over 3000.
Many economists agree the bill's aid is too low but say the immediate support is still welcome and necessary.
A source familiar with the situation said Trump's objection caught many White House officials by surprise. His repeated expression of discontent over it has dashed hopes he would sign.
Trump spent much of Thursday and Christmas Day golfing at his club in West Palm Beach, Florida. The bill has been sent to Mar-a-Lago, his Florida residence.
On Saturday, Trump remained at his Mar-a-Lago club, with minimal staff but with members of his family, including senior advisers Jared Kushner and Ivanka Trump.
According to his daily schedule, he was involved in "many meetings and calls", although the White House did not provide any details.
He has been sending tweets repeating his baseless claims about election fraud and accusing fellow Republicans of abandoning him in his bid to overturn the election result, already shot down multiple times by US courts.
He is yet to acknowledge Biden's victory.
Trump appeared to be in an isolated position on the aid bill as well, with few Republicans voicing support for his position.