Donald Trump will not negotiate with his rivals over the US government shutdown until they "stop playing games", the White House has insisted.
The deadlock, which could go on for weeks, with federal employees facing no pay and being told to stay away from work, is continuing amid a vicious blame game.
While Mr Trump and the Republicans complain that the shutdown is the fault of "filibustering" Democrats who are putting the rights of illegal immigrants before national funding, the Democrats, in turn, are accusing the US President of a "failure in leadership".
White House spokeswoman Sarah Huckabee Sanders said: "The President will not negotiate on immigration reform until Democrats stop playing games and re-open the government."
And Mr Trump himself tweeted: "Democrats are holding our Military hostage over their desire to have unchecked illegal immigration. Can't let that happen!"
Democrats are holding our Military hostage over their desire to have unchecked illegal immigration. Can’t let that happen!
— Donald J. Trump (@realDonaldTrump) January 20, 2018
Republican Senate majority leader Mitch McConnell described it as an "unfortunate hostage situation" and protested about "rhetorical gymnastics" from the Democrats.
"The American people see through this bluster," he said.
And he added: "The solution is to end the foolishness hurting millions of Americans who've done absolutely nothing to deserve this."
The situation reached crisis point when Republican leaders failed to get the 60 votes needed in the Senate to pass a spending bill by midnight on Friday in Washington DC.
The legislation would have provided a fiscal rescue package to keep funding the government until 16 February.
And so technically, the US government has run out of money.
Hitting back, House Democratic leader Nancy Pelosi has angrily accused Republicans of being "so incompetent and negligent that they couldn't get it together to keep the government open".
She said: "The issue is… will they invest in domestic agenda? They're using Daca (the Obama-era scheme allowing undocumented immigrants to stay in the US) as an excuse… they're using is as a shield for their incompetence."
And she added: "We believe in governance – we don't believe in shutdowns."
Democrat Senate minority leader Chuck Schumer, furious at Mr Trump and his party, accused senior Republicans of being afraid to deal with the President and unable to gauge what he is thinking.
Claiming Mr Trump backs off from agreements due to right-wing pressure, he said: "We Democrats are at the table… the President needs to pull up a chair."
The row is continuing exactly a year after President Trump's inauguration.
He cancelled his trip to his Mar-a-Lago resort in Florida, where he was due to be celebrating with a party. Tickets for the bash were reported to have sold for up to $250,000.
Mr Trump earlier tweeted: "This is the One Year Anniversary of my Presidency and the Democrats wanted to give me a nice present. #DemocratShutdown."
Sky News' Washington correspondent Mark Austen said: "What this shows is the dysfunction here in Washington. The political system has ground to halt and it's a very unedifying spectacle indeed."
Also marking one year since Mr Trump was sworn in as president are thousands of women marching in cities across the US against his policies on immigration, abortion, LGBT and women's rights.
In Oklahoma, protesters have been chanting: "We need a leader, not a creepy tweeter!"
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In response to the women's marches, Mr Trump sarcastically tweeted: "Beautiful weather all over our great country, a perfect day for all Women to March.
"Get out there now to celebrate the historic milestones and unprecedented economic success and wealth creation that has taken place over the last 12 months. Lowest female unemployment in 18 years!"