A senior American Air Force commander says daily U.S. military phone calls with Russia have increased as the two countries work to avoid aircraft mishaps in the increasingly crowded skies over Syria.

Air Force Lt. Gen. Jeffrey Harrigian, who is in charge of U.S. air operations in the Middle East, says the U.S. has also set up temporary “deconfliction” zones around Syria. Military operations by Russia or its allies are essentially restricted in those zones so American and U.S.-backed forces are protected.

He declined to say how many exist or where they are. But they signal increased military collaboration as the war on Islamic State militants in Syria escalates.

Harrigian says the talks with the Russians aren’t always easy and sometimes it takes several calls to ensure troops are safe.

(AP)