WASHINGTON - President Donald Trump said Friday that he was considering declaring a national emergency to secure money for a border wall — a move that would curtail Congress on an issue that led to the ongoing government shutdown.

The possibility, first reported by ABC News, is almost certain to face legal challenges if Trump were to elect to make the declaration. During a news conference Friday about negotiations to end the government shutdown, the president told reporters that he was weighing the option, adding "I can do it if I want."

"We can call a national emergency because of the security of our country, absolutely," Trump said.

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A national emergency, declared by the president by proclamation or executive order, gives a president extraordinary powers — to seize property, call up the National Guard and hire and fire military officers at will.

"We can do it. I haven't done it. I may do it," Trump told reporters. "We can call a national emergency and build it very quickly and it's another way of doing it, but if we can do it through a negotiated process, we're giving that a shot."

ABC News reported that some of the options being examined as part of an order would include reprogramming funds from the Department of Defense and possibly other agencies.

Last month, Sarah Sanders said that federal agencies were examining where funds for departments might be able to be reprogrammed to help fund the wall, adding that lawyers at the White House were examining each possibility since it's Congress' job to approve and appropriate federal funding.

After confirming that he was considering the option, Trump was asked if Democrats should take the option as a threat.

"I'd never threaten anybody," Trump said. "But, I am allowed to do that, yes."

Sen. Jack Reed, the top Democrat on the Armed Services Committee, vowed in a statement that he and others would block any attempt by the president to issue an emergency for the funding.

"The idea that President Trump is considering declaring a phony national emergency as a pretext to take billions of dollars away from our troops and defense priorities in order to pay for his wall should alarm all Americans," he said. "Defense spending is for national defense, not the Trump campaign’s political wish list. I will work with colleagues on both sides of the aisle to block any attempt to take money that has been dedicated for our troops and redirect it to construction of a wasteful, ineffective wall."

Reed also questioned the legality of the idea, saying the law only allows the redirection of funds within the military for construction when it's necessary to support the armed forces.

"We are not at war with Mexico, and the proposed border wall has no core DOD function," Reed added.

Presidents have declared scores of emergencies over the past 40 years, dealing with everything from the Iran Hostage Crisis to the Swine Flu. More than 30 of those national emergencies remain in effect.