Update 10pm: Republicans and Democrats showed no signs of ending their stand-off over immigration and spending as Americans woke up to the first day of a government shutdown.
Congress staged a weekend session to show voters it was trying to resolve the stalemate, which led to the closure of many government agencies in a striking display of Washington dysfunction.
However, the day - the first anniversary of Donald Trump's inauguration as president - was marked more by finger-pointing than signs of bipartisan deal-making.
Mr Trump made light of the debacle in a tweet that Democrats "wanted to give me a nice present" to mark the start of his second year in office.
This is the One Year Anniversary of my Presidency and the Democrats wanted to give me a nice present. #DemocratShutdown— Donald J. Trump (@realDonaldTrump) January 20, 2018
The president spoke with Senate Majority Leader Mitch McConnell to discuss the next possible steps, while chief of staff John Kelly also sought an agreement.
White House negotiators, legislative affairs director Marc Short and budget chief Mick Mulvaney, went to Capitol Hill to meet with House Republicans, who emerged holding fast to their stance they would not negotiate while the government was closed down.
Senate Democrats had killed a Republican-drafted House-passed measure that would have kept agencies functioning for four weeks. Democrats were seeking a stop-gap bill of just a few days in the hope it would build pressure on Republicans, and were opposing a three-week alternative offered by Republican leaders.
Democrats have insisted they would back legislation reopening the government once there is a bipartisan agreement to preserve protections against deporting about 700,000 immigrants who arrived in the US illegally as children. Each party believes it has a winning political hand, and the day's first words by party leaders underscored that so far, neither side believe it is time to give ground.
Mr McConnell said: "The American people cannot begin to understand why the Senate Democratic leader thinks the entire government should be shut down until he gets his way on illegal immigration."
Senate minority leader Chuck Schumer said voters will fault Mr Trump and his party. He blamed the president for reneging on a near-deal that Mr Schumer said the two men had approached during a White House meeting yesterday.
"Negotiating with President Trump is like negotiating with Jell-O," Mr Schumer said.
Though the House and Senate were in session today, it was unclear whether legislators would take any votes of consequence.
Democrats said they oppose the three-week plan, viewing it as a way to stall negotiations over the future of the "Dreamers" immigrants, whose protections expire in March. Republicans declared they would not reopen talks until the government shutdown ends, a strategy aimed at trying to erode Democratic cohesion.
Social Security and most other safety-net programs are unaffected by the lapse in federal spending authority. Critical government functions will continue, with uniformed service members, health inspectors and law enforcement officers set to work without pay. But if no deal is reached before Monday, hundreds of thousands of federal employees will be furloughed.
Earlier: Blame game begins as US Government shuts down
Bickering politicians in Washington have failed to keep their government in business, halting all but the most essential operations and marring the one-year anniversary of President Donald Trump's inauguration.
It was a striking display of Washington dysfunction, and the finger-pointing came quickly.
President Trump tweeted that Democrats "wanted to give me a nice present" to mark the start of his second year in office.
The Republican-controlled Congress scheduled an unusual weekend session to begin considering a three-week version of a short-term spending measure and to broadcast to the people they serve that they were at work as the closure commenced.
It seemed likely that each side would push for votes aimed at making the other party look culpable for shuttering federal agencies.
The fourth government shutdown in a quarter of a century began at the stroke of midnight on Friday, last-gasp negotiations crumbling when Senate Democrats blocked a four-week budget extension.
Behind the scenes, however, leading Republicans and Democrats were trying to work out a compromise to avert a lengthy shutdown.
The closure began at the start of a weekend, so many of the immediate effects will be muted for most Americans.
Damage could build quickly if the closure is prolonged. And it comes with no shortage of embarrassment for the president and political risk for both parties, as they wager that voters will punish the other at the ballot box in November.
President Trump said Democrats "could have easily made a deal but decided to play Shutdown politics instead."
In a series of tweets hours after the shutdown began, the president tried to make the case for Americans to elect more Republicans in November "in order to power through this mess".
He noted that there are 51 Republicans in the 100-member Senate, and it often takes 60 votes to advance legislation.
Social Security and most other safety net programmes are unaffected by the lapse in federal spending authority. Critical government functions will continue, with uniformed service members, health inspectors and law enforcement officers set to work without pay.
But if no deal is brokered before Monday, hundreds of thousands of federal employees will be put on hold.
Earlier: US Government shuts down after immigration standoff
The US government shut down at midnight after Congress failed to resolve a partisan standoff over immigration and spending.
In a late-night vote, Senate Democrats blocked a bill that would have kept the government running for another four weeks.
A flurry of last-minute negotiations failed to beat the deadline.
Democrats have tried to use the Friday night funding deadline to win concessions from Republicans, including an extension of an Obama-era program protecting some young immigrants from deportation.
The program is set to expire in March. Republicans sought more time for talks, but Democrats refused.
The shutdown is only the fourth government closure in 25 years. It will only partially curb government operations. Uniformed service members, health inspectors, and law enforcement officers are set to work without pay.