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(CNN) —  

Vice President Mike Pence said Monday that the White House counsel is looking at the President’s ability to declare a national emergency to fund border security, something President Donald Trump has repeatedly said he is considering as partial government shutdown negotiations have reached their third week at a virtual stalemate.

Asked to explain how thoroughly the White House counsel’s office has reviewed the possibility of an emergency declaration, Pence said it is something they have examined, but the administration would prefer to solve the problem of border security funding through Congress.

“What I’m aware of is they’re looking at it and the President is considering it,” Pence told reporters during an hourlong briefing alongside Homeland Security Secretary Kirstjen Nielsen and Office of Management and Budget acting director Russell Vought.

“There’s no reason in the world why the Congress shouldn’t be able to roll its sleeves up and work together to find a principled compromise to address what is a real crisis at our southern border,” Pence added.

The trio repeatedly used the word “crisis” to describe the state of the US-Mexico border as they made the administration’s case for $5.7 billion in border security funding. Democrats have refused to support the spending and Trump has refused to sign legislation reopening the government without it.

“All I know is it’s something they’ve (the White House counsel’s office) looked at, they’ve examined,” Pence said. “There’s no reason in the world why we shouldn’t be able to solve this through the regular legislative process.”

Trump declared Monday morning that there was “no doubt” he had the authority to declare an emergency, but “let’s get our deal done in Congress.”

A source familiar with the matter said the White House counsel’s office had looked at the President declaring a national emergency over the border wall last year when Don McGahn was White House counsel but no conclusion had been reached. The source said the challenge is making the case it’s actually a national security emergency – Trump just saying it doesn’t make it so.

The source added that making the legal case is “not nuts, but it’s not easy.” Part of the concern in the White House counsel’s office is that it would be immediately challenged in the courts, given all the other immigration issues under the administration that are being challenged. The source also said to look for the administration ramping up the use of language such as “crisis” and “invasion” to bolster the case that the border wall funding is a matter of national security.

The word “crisis” was used 37 times during Monday’s hourlong briefing by Pence, Nielson and Vought, according to a White House transcript.

The President initially raised the possibility of declaring a national emergency during Rose Garden remarks on Friday

“I haven’t done it. I may do it,” Trump said. “We can call a national emergency and build it very quickly.”

The President continued to suggest he was considering the possibility on Sunday as weekend negotiations led by Pence failed to yield results, but when asked by reporters upon his return from Camp David if he had a timeline for doing so, he said, “We’ll be letting you know fairly soon.”

The idea has met pushback from some, including California Democratic Rep. Adam Schiff, who said Sunday on CNN’s “State of the Union” that he did not think Trump would be able to use emergency powers to build a wall at the southern border.

“Look, if Harry Truman couldn’t nationalize the steel industry during wartime, this President doesn’t have the power to declare an emergency and build a multibillion-dollar wall on the border,” Schiff said. “So that’s a nonstarter.”

Schiff said the burden remained on Trump to move and reopen the government, saying Trump had painted himself into a corner and needed to “figure out how he unpaints himself from that corner.”

Asked Monday whether a declaration of an emergency should be used as a bargaining chip, Pence said: “There’s no threat going on here.”

Trump is expected to continue to make his case for border wall funding in a national address Tuesday evening, and he will travel to the US-Mexico border on Thursday to “meet with those on the front lines of the national security and humanitarian crisis,” White House press secretary Sarah Sanders announced Monday morning on Twitter.

CNN’s Eli Watkins and Pamela Brown contributed to this report.