US President Donald Trump has renewed a threat to declare a national emergency to fund the construction of a wall on the Mexican border.
A row with Democrats over funding the wall has left the government partially shut down for 20 days, leaving some 800,000 federal employees unpaid.
On Saturday, the shutdown becomes the longest in US history.
Mr Trump says the wall, a key campaign pledge, is needed to tackle a security crisis of illegal immigration.
The Democrats say the wall is an “immorality” and a waste of taxpayers’ money.
President Trump has refused to sign legislation to fund and reopen the government if it does not include $5.7bn (£4.5bn) for the wall.
He issued the threat on a visit on Thursday to a border patrol station in McAllen, in the Rio Grande Valley of Texas.
He said that if Congress did not approve funding for the wall, he would “probably… I would almost say definitely” declare a national emergency to bypass lawmakers.
“I have the absolute right to declare a national emergency,” he said.
Mr Trump would have the right to undertake such a construction project in times of war and national emergency, usually allocating funds from the department of defence.
But bypassing Congress would be hugely controversial, sparking allegations of the overuse of executive powers and it would almost certainly face huge legal challenges.
Some US media reports suggest the White House is considering diverting some of the $13.9bn (£10.9bn) allocated last year by Congress for disaster relief in such areas as Puerto Rico, Texas and California to pay for the wall.
NBC News reported on Thursday that Mr Trump had been briefed on such a plan but the White House denied it.
Analysts say the national emergency move would provide political cover to reopen government while allowing Mr Trump to argue he has done all he can to fulfil his campaign promise.
The BBC’s David Willis in Washington says that, with no further talks with the Democrats planned, this now seems the most likely option for the president.
Republican Senator Lindsey Graham, a key Trump ally, said there was no other pathway forward.