U.S. Government Shut Down Could Drag Past Christmas

On day one of a U.S. government shutdown, President Donald Trump said he was continuing to negotiate with Democrats to end the impasse over the federal budget, but warned, "it could be a long stay".

Trump has demanded $US5 billion ($A7.1b) to help finance construction of a fence along the US-Mexico border, something Democrats in Congress have resisted.

"We are negotiating with the Democrats on desperately needed Border Security (Gangs, Drugs, Human Trafficking & more) but it could be a long stay," Trump said on Twitter on Saturday.

The US Senate and the House of Representatives will be in session on Saturday as congressional leaders try to hammer out a spending agreement to end the stalemate.

Trump also said on Twitter he would be inviting lawmakers to the White House on Saturday to discuss the situation - saying the talks would be on border security - but did not provide details on who would attend.

Senate majority leader Mitch McConnell, speaking on the Senate floor, said no votes would be held until a deal is struck by Democrats and the White House.

"We pushed the pause button until the president, from whom we will need a signature, and Senate Democrats, from whom we will need votes, reach an agreement," McConnell said.

READ MORE: U.S. Government Shuts Down In Fight Over Border Wall

The shutdown went into effect after Trump threw a wrench into the works earlier in the week.

He refused to agree to a short-term funding deal cut by Democratic and Republican senators because it did not include the funds for his border wall.

The US House of Representatives, where Republicans have a majority until Democrats take over on January 3, passed a bill that included the $US5b, but it ran aground in the Senate and the shutdown began at midnight on Friday.

A sign announces the closure of the National Archives building in Washington, DC. Image: AAP

Trump has sought to blame Democrats for the shutdown, while they have repeatedly reminded the president he said last week he would be "proud" to shut the government down.

About three-quarters of federal government programs are funded through to September 30 next year, but the financing for all others expired at midnight.

Federal parks are closed and more than 400,000 federal "essential" employees in those agencies will work without pay until the dispute is resolved.

US President Donald Trump inspects border wall prototypes in San Diego. Image: Getty

Another 380,000 will be "furloughed", meaning they are put on temporary leave.

Law enforcement efforts, border patrols, mail delivery and airport operations will keep running.

For the shutdown to end, both the House and the Senate will have to approve any deal negotiated between Trump's team and Republican and Democratic leaders.

In a joint statement on Saturday, Senate Democratic leader Chuck Schumer and House Democratic leader Nancy Pelosi said that if the shutdown continues, the new House Democratic majority will quickly pass