President Donald Trump said he's considering declaring a national emergency within days in order to build segments of the massive wall along the U.S. southern border as little progress has been made to reopen the federal government, which has been shut down for more than two weeks.

"I may declare a national emergency dependent on what's going to happen over the next few days," Trump told reporters outside the White House ahead of a trip to Camp David, adding that he didn't expect much progress to be made Sunday on ending the shutdown.

Trump first suggested declaring a national emergency to reallocate existing, "un-obligated" Defense Department funds toward the building of a border wall on Friday. Legal experts told NBC News that while such a maneuver to bypass Congress is not out of the question, it is likely to be faced with legal challenges.

Asked by "Fox News Sunday" host Chris Wallace about how serious Trump is regarding such a declaration, White House press secretary Sarah Sanders said simply that Trump is "prepared to do what it takes to protect our borders."

Acting White House chief of staff Mick Mulvaney, speaking on NBC's "Meet the Press," didn't sound optimistic about the possibility of Trump declaring a national emergency, saying "it's not easy to do."

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He added that Trump "made it very clear to every single member of the Cabinet several months ago, 'I need you to go out and find every pot of money that you possibly can'" regarding funding the border wall.

Republican Rep. Liz Cheney of Wyoming told ABC's "This Week" that "nobody wants Trump to invoke" a national emergency "and I don't believe the president wants to invoke it." Instead, she blamed House Speaker Nancy Pelosi for the stalemate.

Democratic Rep. Adam Smith of Washington also told ABC that Trump does have the power to declare such an emergency, but the president would leave the door "wide open to a court challenge saying, 'where is the emergency?'" He added that, on portions of the border where a wall makes sense, it already exists.

Democratic Rep. Adam Schiff, speaking with CNN's "State of the Union," said that Trump actually doesn't have the power to build the wall through such a national emergency declaration, saying that if President Harry Truman couldn't nationalize the steel industry during Korean War, Trump wouldn't have the power to build the additional wall under these circumstances.

Hundreds of thousands of federal employees have been out of work and not receiving paychecks during the shutdown.

Trump said Sunday morning that he could "relate" to those workers who are not receiving pay and may be unable to pay important bills. But the president, who has said that most of those workers are Democrats, again claimed that "many of those people" who aren't receiving paychecks "agree 100 percent with what I'm doing."

Trump said some "serious talks" toward ending the shutdown will take place early this week. On Sunday, Vice President Mike Pence will meet with congressional staffers.

The president added that he is "totally involved" in shutdown negotiations, saying the standoff could end "in 20 minutes" if Democratic leaders wanted it to. Trump has demanded more than $5 billion in funding for the border wall, scuttling a previously agreed upon December funding resolution that would've kept the government open through early February. Democrats have insisted they will not provide Trump with any additional wall funding aside from roughly $1 billion that had been allocated for border wall purposes earlier this year.

Democratic Rep. Colin Allred of Texas, speaking with CBS's "Face the Nation," said Democrats are "willing to negotiate on border security" but "there is a difference though, between border security and then building a wall we don't need" that he called "a waste of money."

On that same program, Republican Sen. Lindsey Graham of South Carolina, an ally of the president, said Trump was open to making a broader immigration deal.

"I do want open the government, but the goal is not to open the government," Graham said. "The goal is to fix a broken immigration system."