The State Department on Thursday cast doubt on reports that Iranian military forces have cooperated with Iraq in a brewing fight with a key U.S. partner in the country.

“I’m not aware of any Iranian involvement in that, per se,” State Department spokeswoman Heather Nauert told reporters Thursday.

Iran’s influence over the central government in Baghdad has alarmed U.S. lawmakers and foreign policy leaders amid an outbreak of infighting. Iraqi Kurds tried to capitalize on their prominent role in driving the Islamic State from the country by voting to form an independent state. The Trump administration has tried to remain neutral while endorsing a unified Iraq, but Iranian military leaders reportedly helped Baghdad take control of a critical city in the region.

“Iran is always a huge concern of ours, not just in Iraq but throughout the region,” Nauert said. “When the Iranian regime shows up, bad things tend to happen.”