By Richard Cowan and Amanda Becker
WASHINGTON (Reuters) - President Donald Trump and Congress, embroiled in a feud over his proposed U.S.-Mexico border wall, have only five days to reach a deal before a partial government shutdown could leave about a quarter of the federal workforce without paychecks.
Trump has demanded $5 billion (3.9 billion pounds) as a down payment on construction of a huge wall that he argues is the only way to keep illegal immigrants and drugs from crossing into the United States, again pushing the proposal in an early morning tweet on Monday. Democrats and some Republicans argue there are less costly, more effective border controls.
The money Trump wants is only a small fraction of the roughly $450 billion Congress was poised to approve - before the latest battle over the proposed wall - to fund several agencies which will otherwise run out of money on Dec. 21.
Large swaths of the government already are funded through next September, including the U.S. military and agencies that operate public healthcare, education and veterans' programs.
Several Republican and Democratic congressional aides on Friday said there was no apparent progress being made towards resolving the standoff, after Trump and leading congressional Democrats battled each other on Tuesday in front of television cameras in the White House Oval Office.
"I am proud to shut down the government for border security," Trump told House of Representatives Democratic leader Nancy Pelosi and Senate Democratic leader Chuck Schumer.
Since then, a senior House Republican aide said his party was "in a pickle" over how to keep the government open.
The aide noted that Republicans, who will control both houses of Congress until Jan. 3, will not be able to muster the minimum 218 votes needed in the House to pass a funding bill if it contains Trump's demand for border wall money, which Democrats oppose.
If funds run out on Dec. 21, the NASA space programme would potentially be unfunded, along with national parks, the U.S. diplomatic corps and agriculture programs.
Similarly, the Department of Justice and the Department of Homeland Security would be vulnerable to shutdowns, although "essential" employees, such as FBI agents, airport security screeners and border patrol agents, would still report to work.
Their paychecks, however, would not be issued until the shutdown ends and Congress would have to decide whether to award back pay for them as well as any furloughed workers.
A government in such disarray might not play well for Republicans over the holiday period, especially if Americans also view images for two weeks of Trump vacationing at his exclusive Florida beach-front mansion.
"After the president’s comments earlier this week when he said he was going to own the shutdown, that sealed the deal for Democrats. There is absolutely no reason for them to cut a deal with this president," said Jim Manley, a political strategist and former Senate Democratic leadership aide.
With the clock ticking, the House is not even bothering to come to work until Wednesday night.
For now, Democrats are waiting for the White House to signal whether it will engage on legislation that would keep programs operating, but without money for Trump's wall.
White House adviser Stephen Miller told CBS News' "Face the Nation" programme on Sunday that the administration would "do whatever is necessary to build the border wall." Asked if that included shutting down the government, he said: "If it comes to it, absolutely."
If not, Manley predicted the government will limp along until Jan. 3, when Democrats take control of the House and Pelosi likely becomes the speaker and promptly advances funding, daring the Republican-led Senate to reject it.
(Reporting by Richard Cowan and Amanada Becker; Additional reporting by Susan Heavey; Editing by Kevin Drawbaugh, Leslie Adler and Paul Simao)