Russian reconnaissance flights over Iraq to spy on Islamic State militants would complicate the U.S.-led campaign against the extremist group but wouldn’t obstruct it, American officials said Monday after Baghdad left open the possibility of overflights by Moscow.

At the same time, U.S. ability to share intelligence with Iraq could be diminished if the Iraqis are sharing information with the Russians, American defense officials said.

An Iraqi defense ministry spokesman said Monday that his country would be open to Russian intelligence gathering in Iraqi airspace. […]