WASHINGTON — Five days ahead of the latest funding deadline, acting White House Chief of Staff Mick Mulvaney said Sunday that he "absolutely cannot" rule out the possibility of another partial government shutdown if Congress doesn't come to an agreement that includes substantial funding for a border wall.

Mulvaney blamed the uncertainty on congressional Democrats, arguing that Democrats appear torn between the "hard-core left wing," which sees any funding for President Donald Trump's signature border wall as a non-starter, and a more moderate faction that appears open to compromise.

"Let's say the hard-core left wing of the Democrat Party prevails in this negotiation and they put a bill on the president's desk with, say, zero money for the wall, or $800 million, an absurdly low number. How does he sign that?" Mulvaney said on "Meet the Press."

"You cannot take a shutdown off the table, and you cannot take $5.7 billion off the table," he added, referring to Trump's initial price tag for the wall.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

But he said the "most likely outcome" would be that Congress strikes a deal palatable enough to win the president's signature.

"If you end up some place in the middle, yes, then what you'll probably see is the president say: 'Yes, OK. And then I'll go find the money some place else'" to fully fund a wall.

Sen. Richard Shelby, R-Ala., chairman of the Appropriations Committee, said on "Fox News Sunday" that "talks are stalled" and that there's a "50/50 chance" that Congress can reach a deal to avoid shutting the government down for the second time in two months.

The wall remains the largest sticking point in these negotiations. Trump still says the wall is necessary. But House Speaker Nancy Pelosi, D-Calif., has so far held firm on her party's opposition to its funding.

House Democratic leader Steny Hoyer of Maryland accused Mulvaney on Sunday of "threatening another unnecessary and dangerous government shutdown," calling his remarks "irresponsible and alarming." He said House Democrats would continue to oppose funding for "a costly and unnecessary wall that does not make us safer or address the humanitarian challenges on our border.”

A senior Democratic aide told NBC News that there are other major debates to be solved, including a Democratic push to trade funding for new border barriers for a limit on Immigration and Customs Enforcement's detention beds as a way to push back at the administration's border policies.

Trump pointed to unanswered questions in debates like those while sharing his own skepticism about the chances of a deal in a tweet Sunday morning.

I don’t think the Dems on the Border Committee are being allowed by their leaders to make a deal. They are offering very little money for the desperately needed Border Wall & now, out of the blue, want a cap on convicted violent felons to be held in detention! — Donald J. Trump (@realDonaldTrump) February 10, 2019

Republicans and Democrats have until Friday to find an agreement thanks to last month's deal that lifted the historic 35-day partial shutdown.

Even if Congress passes something Trump supports, Mulvaney described any deal as the beginning, not the end, of Trump's efforts to build the wall he believes is necessary to secure America's southern border. One option floated by the president and his allies is to declar a national emergency to secure the funding, but it's unclear whether that would survive a legal challenge.

"The president really does believe that there is a national security crisis and a humanitarian crisis at the border, and he will do something about it. So whether or not he gets $1.6 billion from Congress, whether or not he gets $2.5 [billion] or $5.7 [billion], he's going to do whatever he legally can to secure that border," Mulvaney said.

"There are pots of money where all presidents have access to without a national emergency. And there are ones that he will not have access to without that declaration."