House Speaker Paul Ryan is leading a delegation of lawmakers to the U.S.-Mexico border this week as Congress debates how to pay for President Trump’s campaign promise to build a wall to keep out undocumented immigrants.

It will be the first trip to the U.S-Mexico line for the Wisconsin Republican, who arrived in Texas on Monday to attend a fundraiser with members of the state’s GOP delegation. On Wednesday, Ryan is scheduled to visit the U.S. Border Patrol station in McAllen for a daylong tour of the Rio Grande Valley. With a small group of House Republicans led by top Homeland Security officials, Ryan will “examine the challenges of securing our border and learn more about the issues facing border communities,” spokeswoman AshLee Strong said.

The delegation will include Rep. Michael McCaul, R-Texas, chairman of the House Committee on Homeland Security.

Ryan’s trip comes as Trump’s pledge to reshape the U.S. immigration system and Congress’ role in funding the plan take center stage in the new administration.

On Tuesday, with the administration’s travel ban blocked by the courts for now, Homeland Security officials released new guidelines that allow federal authorities to take stronger enforcement actions against undocumented immigrants.

Meanwhile, Congress is beginning to assess the cost of building a border wall, the president’s signature campaign promise. Trump has vowed to make Mexico cover the cost, but the Mexican government has balked at that plan. Right now the project has no reliable price tag. Trump has estimated the cost at $8 billion. Recent congressional legislation pegged the number at $10 billion, and construction experts say it could be more than double that.