Washington(CNN) A holiday government shutdown appeared more likely on Thursday after President Donald Trump informed House Republicans he would refuse to accept a stop-gap measure -- already passed by the Senate -- that doesn't include funds for his long-promised border wall.

What was once a deal to avoid a Christmas partial shutdown was torpedoed Thursday by conservatives and Trump, who unleashed fury at another agreement that stops short of providing the $5 billion the President has demanded for the border.

It was a closing burst of wrath in the final days of the Republican-majority House. If Trump cannot secure the money he is demanding for the wall now, it's unlikely he will see a spending bill that meets his requirement for at least two years as Democrats assume control.

The uncertainty sent lawmakers scrambling to devise a solution that could keep funds flowing to some government agencies after Friday's deadline. It's not clear if there are enough votes in the House for a bill that would include the $5 billion in border wall funding; in the Senate, where any measure will require 60 votes to clear procedural hurdles, there are almost certainly not enough votes.

Stewing at the White House, Trump ranted on Twitter that he'd been down a similar road earlier this year, only to find himself again in the same position. His press secretary said he wouldn't move forward without the billions in funding for "steel slats or a wall."

He summoned House Republicans -- who thought they'd struck a deal to avert a shutdown -- for noontime talks at the White House.

"President Trump just met with Republican Members of the House. Not surprisingly, they all feel strongly about border security -- stopping the flow of drugs, stopping human trafficking and stopping terrorism. We protect nations all over the world, but Democrats are unwilling to protect our nation. We urgently need funding for border security and that includes a wall," White House press secretary Sarah Sanders said following the White House meeting.

Stocks, already trading lower because of the Federal Reserve's Wednesday decision to raise its benchmark interest rate, were sharply down as the scramble in Washington appeared to be leading toward a shutdown.

The White House is following Office of Budget and Management guidelines on notifying federal employees whether they'll be furloughed in case of a government shutdown, a senior administration told CNN's Jim Acosta.

"Prudent management requires that agencies be prepared for the possibility of a lapse. OMB guidance states that two business days before a potential lapse, agencies need to notify employees of their work and pay status under a lapse -- that is, if they are furloughed or excepted. Agencies were directed by OMB to start that notification this morning," the official said.

The last-minute scramble came after several days of whiplash, which began last week when Trump said in a meeting with Democrats that he would be proud to oversee a shutdown if it meant securing funds for the wall.

Later, the White House signaled he was softening on that stance, indicating the President was open to a compromise that fell short of providing the $5 billion Trump is demanding.

That provided an opening for Republican lawmakers to begin proceedings on a measure that would provide funding for nine federal agencies through February. That bill passed the Senate on Wednesday evening.

But on Thursday morning, the future of that plan was thrust into question after Trump tweeted his frustration at having to swallow another spending measure that doesn't include funds for the wall.

State of play

The Senate-passed plan would have provided funding through February 8 -- after Democrats assume control of the House, making this Trump's last chance to secure wall funding.

"When I begrudgingly signed the Omnibus Bill, I was promised the Wall and Border Security by leadership. Would be done by end of year (NOW). It didn't happen!" he wrote after a phone conversation with House Speaker Paul Ryan. "We foolishly fight for Border Security for other countries - but not for our beloved U.S.A. Not good!"

Trump remained ambiguous Thursday on whether he will sign a measure temporarily funding the government in order to avoid a year-end shutdown, as he lamented a lack of funding for his desired border wall.

He is due to depart Friday afternoon for an extended holiday stay at his Mar-a-Lago estate in South Florida. The White House has refused to say whether he would still travel there if the shutdown occurs. Included in the federal agencies affected would be the Secret Service, whose agents and officers would still work to protect the President and his family, just on an unpaid basis.

A senior White House official told CNN Friday it's possible that Trump will decide not to back down on the wall fight as a result of growing pressure from the Freedom Caucus and conservatives.

The official said it's still unclear what Trump will do -- a similar situation to the omnibus signing last March.

"If Congress can't give the President border wall funding now with Republicans in charge we certainly don't stand a chance with (House Democratic Leader Nancy) Pelosi and the Dems taking over the House next year," the official said.

Mixed signals

The President has sent mixed signals for the past week on whether he would sign the legislation that would stave off a shutdown of some key federal agencies, set to expire at midnight on Friday, just days before Christmas.

"The Democrats, who know Steel Slats (Wall) are necessary for Border Security, are putting politics over Country. What they are just beginning to realize is that I will not sign any of their legislation, including infrastructure, unless it has perfect Border Security. U.S.A. WINS!" Trump tweeted Thursday, seeming to indicate he would pick up the border wall fight next year after Democrats take control of the House.

While the legislation, which passed the Senate Wednesday, is expected to pass the House before the end of the week, many conservatives are calling on the President to oppose the legislation and Trump is listening. But a House Republican leadership news conference was delayed Thursday morning as lawmakers debated how to proceed, lending even more uncertainty to how the issue would get resolved.