WASHINGTON (AP) — Homeland Security Secretary Jeh Johnson is making the case to Congress for President Barack Obama's request for $3.7 billion to deal with a flood of unaccompanied child immigrants that's overwhelming the Border Patrol in South Texas.

Johnson's scheduled appearance Thursday before the Senate Appropriations Committee comes a day after Obama met in Dallas with Texas Gov. Rick Perry, a staunch critic of the president's handling of what Obama has called an "urgent humanitarian situation" at the border.

More than 57,000 children, mostly from Central America, have been caught crossing the border without their parents since October.

Arizona Sen. John McCain and other Republicans made it clear Wednesday that Obama's budget request would be a hard sell.