They’re concerned that the Russian fighters — who are stationed at the same air base as American troops in the capital of Niamey — will engage in disruptive behavior such as driving aggressively or harassing U.S. troops at checkpoints, according to two officials familiar with Western intelligence.

U.S. troops and the Russian military have been nearly operating side-by-side in the African country of Niger for several weeks as tensions over fighting Islamic extremists heat up in the region, officials said.

Russian military personnel have entered an air base in Niger that is hosting U.S. troops, a senior U.S. defense official told Reuters, a move that follows a decision by Niger's junta to expel U.S. forces.