A few hours after President Donald Trump again said a wall must be part of any effort to secure the southern border with Mexico, House Speaker Nancy Pelosi gave the back of the hand to the President's signature campaign pledge, bluntly predicting to reporters that House-Senate negotiators will not produce a deal with wall funding.

"There's not going to be any wall money in the legislation," Pelosi said at her weekly news conference.

Pelosi did not entirely close the door on new border fencing, saying if it's appropriate, then such plans could be part of an overall legislative solution as Congressional negotiators work out a plan to fund the Department of Homeland Security for 2019.

"Is there a place where enhanced fencing - Normandy fencing - would work?" Pelosi said of the work of lawmakers trying to broke a deal on border security funding. "Again, let them have that discussion."

During a photo opportunity in the Oval Office an hour later, the President fired back at the Speaker, as he talked of new illegal immigrant caravans forming in Central America, and moving toward the U.S. southern border.

"If there's no wall, it doesn't work," Mr. Trump said. "Without a wall, it doesn't work."

"Nancy Pelosi will be begging for a wall," the President told reporters.

In his Thursday afternoon exchange with reporters, Mr. Trump repeatedly said he was already building sections of the wall along the Mexican border - which is not accurate - as he once more made clear that he would accept nothing less than a DHS funding bill with wall money.

"If they don't have a wall, I don't even want to waste my time reading what they have," the President said of the work of House-Senate negotiators.

If there's no agreement satisfactory to the President, he has already indicated he would consider declaring a national emergency, and trying to move money around in the federal budget, which could then fund construction of a wall.

"Because he has been unable to get Mexico to pay for his wall, President Trump wants to run it through executive fiat instead," said Rep. Lloyd Doggett (D-TX).

But some Republicans warned that if the President used that authority - and moves to expand the powers of the Executive, Democrats would be more than happy to use those expanded authorities one day when they are back in power.

"They love the idea, currently championed by many Republicans, that “emergency” has no meaning — that the President alone defines it," said Rep. Justin Amash (R-MI). "They can’t wait for him and other Republicans to ratify that view."

Asked if he would declare a national emergency in order to build his wall, the President didn't miss a beat.

"I would do that," Mr. Trump said.