Recriminations have begun over the failure of the United States Senate to pass a new budget and prevent the shutdown of many federal services.
A bill to fund the federal government for the coming weeks did not receive the required 60 votes by the deadline of midnight on Friday.
President Trump accused the Democrats of putting politics above the interests of the American people.
The Democrats blame him for rejecting bipartisan compromise proposals.
Both the Republican and Democrat congressional leaders say they will keep talking, and the White House budget chief has expressed optimism that a resolution will be found soon.
But hundreds of thousands of federal workers are facing the prospect of no work and shuttered offices on Monday morning.
The last government shutdown was in 2013, and lasted for 16 days.