The US government has begun shutting down of many of its services after the Senate failed to agree on a new budget.
A bill to fund the federal government until 16 February did not receive the required 60 votes amid a bitter dispute over immigration and border security.
It is the first shutdown ever to happen while the same party, the Republicans, controls Congress and the White House.
The impasse will affect hundreds of thousands of federal workers, and the recriminations have already begun.
The White House accused Democrats of “[putting] politics above our national security, military families, vulnerable children, and our country’s ability to serve all Americans”.
But the leading Senate Democrat, Chuck Schumer, said President Trump had turned down two bipartisan compromise deals and “did not press his party in Congress”.
The last government shutdown was in 2013, and lasted for 16 days.
What is a government shutdown?
As of 00:01 Saturday, many federal agencies are no longer open for business – although essential services will continue to run.
.@realDonaldTrump should heed his own words:
“if there is a shutdown I think it would be a tremendously negative mark on the president of the United States. He's the one that has to get people together.” #TrumpShutdown pic.twitter.com/pqbGAQf1Tx— Chuck Schumer (@SenSchumer) January 19, 2018
Most staff in the departments of housing, environment, education and commerce will stay at home. Half of workers in the treasury, health, defence and transportation departments will also not be going to work on Monday.
National parks and monuments could face closure, which provoked an angry public reaction during the last shutdown in 2013.
Visa and passport processing could also be delayed.
But essential services that protect “life or human property” will continue, including national security, postal services, air traffic control, inpatient medical services, emergency outpatient medicine, disaster assistance, prisons, taxation and electricity generation.
Why can the two sides not agree?
The main bone of contention has been Democrats’ demands for more than 700,000 undocumented immigrants who entered the US as children to be protected from deportation.
These “Dreamers”, as they are known, were granted temporary legal status under a programme established by former President Barack Obama.
In September, Mr Trump announced he was ending the programme and allowing Congress until March to come up with a replacement.
The Republican president and congressional conservatives have been using the issue as a bargaining chip in an attempt to wring concessions from Democrats.
Mr Trump wants funding for tough new border controls, including his proposed US-Mexico wall.
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Republicans added a sweetener to the bill in the form of a six-year extension to a health insurance programme for children in lower-income families.
But Democrats want this programme extended permanently.
The legislative negotiations went up in flames last week after Mr Trump allegedly complained the US was letting in immigrants from certain “shithole countries”.
What happened during the 2013 shutdown?
Many federal employees were forced to take a leave of absence – officially known as being furloughed – during the 16 days of shutdown.
At its peak, some 850,000 employees were off work each day. The cost, in salaries alone, was $2bn and led to “significant negative effects on the economy”, according to the Office of Management and Budget.
At the time, Donald Trump laid the blame for the shutdown with the then president, Barack Obama.
“The problem start from the top and have to get solved from the top,” he told Fox and Friends. “The president is the leader, and he’s got to get everybody in a room and he’s got to lead.”
