McConnell, Ryan Say Congress Will Pay for Trump's $12B Border Wall Trump paved the way for a wall by signing an executive order.

 -- House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell said today that Congress will forge ahead with plans to approve funds for President Donald Trump's border wall, which they estimate will cost $12 billion to $15 billion.

"We intend to address the wall issue ourselves, and the president can deal with his relations with other countries on that issue and others," McConnell told reporters at a GOP policy retreat in Philadelphia.

On Wednesday, Mexican President Enrique Pena Nieto said his country would not pay for the project after Trump told ABC's David Muir that Mexico would pay the U.S. back "100 percent."

Trump tweeted this morning, "If Mexico is unwilling to pay for the badly needed wall, then it would be better to cancel" a planned Jan. 31 meeting with Pena Nieto.

Ryan promised that building the wall along the U.S.-Mexico border will not add to the federal deficit.

He said he expects Congress to address the wall in a supplemental funding bill after a formal request from the White House.

Trump signed an executive order Wednesday directing construction of the wall.

Ryan and McConnell are leading congressional Republicans on a three-day policy retreat in Philadelphia, where lawmakers are reviewing their 200-day legislative agenda and plans for health care and tax reform.

Trump and Vice President Mike Pence will address the gathering this afternoon. Republicans will also hear from British Prime Minister Theresa May.

ABC's MaryAlice Parks and Ali Rogin contributed to this report.