Democrats in the House and Senate said Tuesday they would oppose any changes to a 2008 human trafficking law Republicans have blamed for the wave of child immigrants crossing the border.

The opposition sets up a standoff and raises serious doubts about whether Congress will be able to act before its summer recess in response to what both parties argue is a humanitarian crisis.

Sen. Tom Harkin (D-Iowa) said he would work to make sure any changes to the 2008 law do not make it into a final funding package.

“The 2008 law, as you know, sets up a reasonable standard for requesting asylum,” he said. “That should never be changed.”