Arizona Sen. John McCain returned from a secret visit to the Syrian border in Jordan this week, where he met with Syrian refugees fleeing the civil war.

McCain is leading a bipartisan congressional group urging President Barack Obama to provide U.S. aid to civilians and government rebels in Syria.

McCain, who also visited Afghanistan as part of a bipartisan Senate delegation, said he heard from refugees who told him anger is growing among Syrians who believe the U.S. isn’t doing enough to support rebel groups fighting Syrian President Bashar Al Assad’s military front.

McCain said the United States needs to do more to pressure for regime change in Syria.

“If we wish to be relevant to the conflict in Syria, we must have a serious debate about how nations can prevent Assad from massacring with fighter jets and helicopter gun ships and even SCUD missiles,” he said in a news conference broadcast on C-Span.

A State Department spokeswoman said Obama is wary of military involvement in Syria, adding that administration officials are confident that Assad’s rule over Syria will end soon.