WASHINGTON — A U.S. warplane shot down an armed drone linked to Syrian regime forces, the Pentagon said Tuesday, the latest in a series of incidents between U.S.-backed forces and the regime of Bashar Assad that threatens to escalate the conflict there.

The drone, an Iranian-built Shaheed-129, was shot down by an F-15E Strike Eagle after it “displayed hostile intent and advanced on coalition forces,” the U.S. military said in a statement.

The incident occurred in the same vicinity as previous conflicts with pro-regime forces, near the combat outpost in At-Tanf, where a contingent of U.S. and coalition advisers are supporting a force to fight the Islamic State, also known as ISIS.

The U.S. action also comes two days after a U.S. warplane shot down a Syrian plane that was attacking U.S.-backed forces near Raqqa, the Islamic State’s de facto capital.

On Sunday, a U.S. Navy F/A-18 warplane shot down a Syrian…