WASHINGTON (Reuters) - Brett McGurk, U.S. President Barack Obama's special envoy in the fight against Islamic State, said on Tuesday he has seen no "significant" change in Iran's behavior in Syria under the international nuclear deal announced last July.

"I have not seen a significant change in Iranian behavior ... They are primarily working to prop up the Assad regime," McGurk told a U.S. Senate hearing. He said Iran is also supporting some Shi'ite militia groups that are operating in Iraq.

(Reporting by Patricia Zengerle; Editing by Jeffrey Benkoe)