It has been four months since U.S. President Donald Trump ordered cruise missile strikes against a Syrian airfield after an alleged chemical weapons attack.

In June, the U.S. military shot down a Syrian fighter aircraft, the first U.S. downing of a manned jet since 1999, and also shot down two Iranian-made drones that threatened U.S.-led coalition forces.

All the while, U.S. and Russian military officials have been regularly communicating, U.S. officials told Reuters.