McConnell, Ryan Say Congress Will Pay for Trump's $12B Border Wall

Trump paved the way for a wall by signing an executive order.

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 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.