The House of Representatives' Homeland Security Committee chairman raised concerns about Donald Trump's praise for Russian President Vladimir Putin.
"I think I would urge caution," Rep. Michael McCaul said. "The idea that Russia is somehow a friend of ours, or that Putin is a friend, is a false narrative. They're not our friends."
McCaul, a Texas Republican, said he does not believe the U.S. can trust Russia.
"I think we do have a common enemy — the Russians don't like Islamic jihadists – but we can't really trust them," he said, as The Hill reported.
U.S. officials have claimed Russia is working with Syrian President Bashar Assad.
"Their No. 1 objective there is to reinforce Assad's stability," McCaul said.
Republican presidential candidate Trump called Putin a better leader than President Barack Obama during an NBC interview. He said having Putin as an ally would benefit the U.S. in the fight against ISIS.
"The beautiful part of getting along — Russia wants to defeat ISIS as badly as we do," Trump said in the interview. "If we had a relationship with Russia, wouldn't it be wonderful if we could work on it together and knock the hell out of ISIS?"
McCaul also has shared criticism of Democratic presidential candidate Hillary Clinton. In July, he launched a bill that could revoke the security clearance of anyone who exercises "extreme carelessness" such as she was accused of amid her email controversy.