US President Donald Trump plans to declare a national emergency in an attempt to fund his controversial US-Mexico border wall without congressional approval.
"The president is once again delivering on his promise to build the wall, protect the border, and secure our great country," White House spokeswoman Sarah Sanders said on Thursday.
Sanders added that the president had also agreed to sign a funding bill that lacks money for his wall but prevents another damaging government shutdown.
Trump’s announcement, expected to be made on Friday, will likely plunge him into a Supreme Court battle against Congress over constitutional powers.
Trump had long floated the possibility of declaring a national emergency, threatening to do so if Congress did not provide him with $5.7 billion for the wall.
"If this doesn't work out, I probably will do it, I would almost say definitely," the president said of a national emergency declaration when he visited the border in Texas last month, adding, "If we don't make a deal, I would say 100 percent, but I don't want to say 100 percent."
The Speaker of the US House of Representatives, Nancy Pelosi, who is the top Democrat in the lower chamber, denounced the president's proposed move.
Asked whether she was willing to take court action against Trump, Pelosi said: "I may, that's an option."
Top Senate Democrat Chuck Schumer criticized Trump for committing what he described as a "gross abuse of the power."
An emergency declaration could infringe on Congress' authority to make major decisions about spending taxpayer funds, a power spelled out as a fundamental check and balance in the US Constitution.
Congressional aides said House Democrats were expected to file a lawsuit after Trump declares an emergency. The short-term result of that could be a court injunction blocking any diversion of funds while judges weigh the matter, possibly leading in a few months to a Supreme Court decision.
Meanwhile, the Senate passed the government funding legislation by a margin of 83-16. The House was expected to take it up later on Thursday. The measure would provide more than $300 billion to fund the Department of Homeland Security and other agencies through September 30, the end of the current fiscal year.
Funding for those agencies is due to expire on Friday, which would trigger another partial federal shutdown on Saturday morning if Congress and Trump failed to act.
The funding bill provides $1.375 billion for 55 miles (88 kilometers) of Trump’s wall, all of it in the Rio Grande Valley in the state of Texas, the busiest corridor for illegal crossings by far.
Trump triggered the previous shutdown of about a quarter of the federal government with his December demand for $5.7 billion in wall money. In opinion polls, Thump was widely blamed for the shutdown in the area.
In denying funding for the border wall, Congress has stood in the way of Trump's vowing to deliver on his 2016 main campaign promise.
Some of Trump's fellow Republicans have warned against declaring a national emergency.
They fear that the move could set a dangerous precedent, opening the door for a future Democratic president to circumvent Congress and declare emergencies on perhaps of world issues including climate change or healthcare insurance.