The top Republican congressional leaders said Thursday they will make available billions of dollars to build the U.S.-Mexico border wall that President Trump ordered via executive action a day earlier.

“We are on the same page,” House Speaker Paul Ryan, R-Wis., said of the agenda being pursued by Trump and the GOP-led Congress.

While Trump’s executive measures on border security left the specifics of the wall’s funding unclear, Ryan and Senate Majority Leader Mitch McConnell, R-Ky., vowed complete cooperation, as they addressed reporter questions on the sidelines of their annual Republican congressional retreat in Philadelphia.

“We intend to address the wall issue ourselves,” McConnell said.

Trump’s order, signed Wednesday, directed Homeland Security Secretary John Kelly to “immediately plan, design and construct a physical wall along the southern border.’’

Some of the border already has a wall or other type of fencing, but hundreds of miles worth of work would have to be done to fulfill Trump’s goal.

Ryan and McConnell said Thursday the project could cost between $12 billion and $15 billion, and Congress would pursue allotting the money under a 2006 law signed by President George W. Bush.

“We are going to finance the Secure Fence Act,” Ryan said, in reference to that law.

Ryan also said addressing the illegal immigration problem can be accomplished through executive actions, “just like the last administration” – referring to executive orders by former President Obama that protected some illegal immigrants from deportation.

Ryan suggested some of the remaining money for the wall could come from the Trump administration. He also argued such a project would not add to the budget deficit, saying “we are fiscal conservatives,” and that congressional Republicans will “by the end of 2017 have made good on the goals and policies we ran on.”

Trump is scheduled to speak at noon with lawmakers in Philadelphia.

The annual retreats typically are low-key events in which lawmakers, many in short-sleeves or jeans, meet in closed-door sessions to hammer out policy issues and draft a game plan for the year, talking to reporters on the side.

However, Trump’s visit this year, and a speech Thursday evening by retired NFL Super Bowl champion Peyton Manning, has attracted nearly 100 reporters, hundreds of protesters and a large security detail.

Ryan said GOP congressional leaders’ ambitious 2017 goals have forced them to move from a 100- to a 200-day agenda, with the economy, tax reform and repealing and replacing ObamaCare at the top of the list.

“If we can fix health care … and get people back to work, that will dramatically improve our budget situation,” he said.

The comments come as Trump not only prepares to seek the money from Congress for a border wall, but continues to insist that Mexico, eventually, will reimburse American taxpayers.

Mexican President Enrique Peña Nieto said Wednesday that Mexico “will not pay” for a wall and that he rejects Trump’s decision to pursue its construction.

Trump took to Twitter on Thursday threatening to nix a meeting with his Mexican counterpart.

He wrote: “The U.S. has a $60 billion trade deficit with Mexico. It has been a one-sided deal from the beginning of NAFTA with massive numbers…of jobs and companies lost. If Mexico is unwilling to pay for the badly needed wall, then it would be better to cancel the upcoming meeting.”