With the federal government set to run out of money at midnight Friday, the president added to the chaos with a burst of early morning tweets.
He second-guessed Republican leaders in Congress and slapped down his own chief of staff who had been leading a White House push on Capitol Hill for a budget compromise.
Arriving at the Pentagon for a visit, Trump told reporters the government "could very well" shut down Friday.
The House of Representatives was expected to vote as early as Thursday on a short-term funding measure, but it was unclear if Republicans had the votes to prevail.
In the event of a shutdown, federal employees for agencies considered non-essential are ordered to stay home until a budget deal is struck, at which point they are paid retroactively. The most recent shutdowns -- in 1995, 1996 and 2013 -- saw some 800,000 workers furloughed per day.
Key government bodies such as the White House, Congress, State Department and Pentagon would remain operational, but would likely furlough some staff. The military would still report for duty, but troops -- including those in combat -- would potentially not be paid.
The finger-pointing had already begun, with each side blaming the other for a failure to reach a budget compromise after three previous funding extensions.
"A government shutdown will be devastating to our military... something the Dems care very little about!" Trump tweeted.
And yet in another tweet, Trump criticized the Republican short-term funding measure, opposing a sweetener intended to make it hard for Democrats to vote against it.
House Speaker Paul Ryan said later he had spoken to the president, and insisted: "He fully supports passing what we're bringing to the floor today."
The sweetener is a six-year extension of a popular children's health insurance program, known as CHIP, a program Democrats have worked hard to protect.
But Trump insisted: "CHIP should be part of a long term solution, not a 30 Day, or short term, extension!"
Republican Senator John Cornyn quickly corrected Trump in a counter-tweet: "The current house Continuing Resolution package has a six-year extension of CHIP, not a 30 day extension."
Nancy Pelosi, the top Democrat in the House, dismissed the Republicans move on CHIP as "like giving you a bowl of doggie doo, put a cherry on top sundae. This is nothing.
"This CHIP should have been done in september," she told reporters.
Many Democrats are already opposed to another short-term fix, leaving Republicans to rely on their own divided caucus to advance the measure.
If it fails, Democrats will gain greater leverage to insist on a funding compromise that includes protection from deportation for the so-called "Dreamers," the estimated 700,000 immigrants brought to the United States illegally as children.
Negotiations on a bipartisan compromise that includes a fix on DACA, as the Deferred Action on Childhood Arrivals program is known, collapsed in acrimony at a White House meeting last week.
Trump's reported reference to African nations and Haiti as "shithole countries" ignited a still smoldering political firestorm.
White House chief of staff John Kelly met Wednesday with the Congressional Hispanic Caucus to make the case that Trump had "evolved" on his signature campaign promise to build a wall the length of the US border.
Funding for border security, but not a full-blown wall, was part of the bipartisan budget compromise presented at last week's contentious White House talks.
Participants at the meeting with Kelly quoted the retired general and former head of the Department of Homeland Security as saying Trump was not "fully informed" when he made the wall promise.
But Trump hit back on Twitter Thursday. "The Wall is the Wall, it has never changed or evolved from the first day I conceived of it," he wrote.
"If there is no Wall, there is no Deal!" Trump said in another tweet that described Mexico as "now rated the most dangerous country in the world."
Mexico once again said it would not pay for the wall, despite Trump's repeated insistence that it will.
The mixed messages from the White House prompted a rebuke Wednesday from frustrated Senate Majority Leader Mitch McConnell.
"I'm looking for something that President Trump supports, and he's not yet indicated what measure he's willing to sign," McConnell told reporters.
"As soon as we figure out what he is for, then I would be convinced that we were not just spinning our wheels."
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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