Some conservative U.S. Republican lawmakers want to tie President Barack Obama's Syrian refugee resettlement program to a spending bill that must pass in order to keep the federal government open after the fiscal year ends on Sept. 30.

In a move that could complicate congressional leaders' efforts to pass the bill on time, members of the House of Representatives' conservative Freedom Caucus said they would support a temporary spending measure if it includes a moratorium on admitting the Syrians to the United States.

Republican Rep. John Fleming, a caucus member, said putting limits on Syrian refugees is a "high priority" for the group. "We should not be allowing refugees from terrorist regions of the world, without proper vetting," he told reporters.