The US government is heading towards a partial shutdown after Republicans in the Senate failed to secure the votes needed to approve $5bn demanded by Donald Trump for a border wall.
Vice President Mike Pence and White House officials were on Capitol Hill on Friday night trying to broker a compromise over funding for the wall on the Mexico border, which is staunchly opposed by Democrats.
Without a deal, funding for around 25% of the government will expire at midnight (5am GMT).
Nine cabinet-level departments and dozens of agencies, including homeland security, transportation, interior, agriculture, state and justice will be affected by the shutdown.
Mr Trump had said any impending shutdown could last "a very long time" as he blamed Democrats over the failure to agree a deal on spending.
He said: "This is our only chance that we'll ever have, in my opinion, because of the world and the way it breaks out, to get great border security."
Democrats will take control of the House in January, and oppose major funding for construction of any wall along the border with Mexico.
Congress had been on track to fund the government, but changed direction when Mr Trump – after criticism from conservative supporters – declared he would not sign a bill if it did not include billions to fund the wall.
He said: "We're totally prepared for a very long shutdown," adding there was strong support for border security "the barrier, wall or steel slats – it's all the same".
Senate Democratic leader Chuck Schumer told the Senate: "President Trump has thrown a temper tantrum and now has us careening towards a 'Trump shutdown' over Christmas.
"You're not getting the wall today, next week or on January 3rd, when Democrats take control of the House."
A partial government shutdown would see staff at affected agencies limited to those deemed "essential" to public safety.
Those workers, including US border agents, would not get paid until the dispute was resolved.
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The wall was a key promise during Mr Trump's 2016 election campaign, which he insisted would be paid for by Mexico.
It comes amid tension in Washington following Mr Trump's decision to withdraw US troops from Syria, which prompted the resignation of defence secretary Jim Mattis.