The Observatory said the U.S. convoy was confronted by villagers and pro-government gunmen who threw stones at the force.
State TV said the convoy was forced to “go back to where it came from.”
A video aired on state TV showed several American armored vehicles flying U.S. flags being chased by men and boys on an unpaved road.
There was no immediate comment from the U.S. military.
Hundreds of U.S. troops are stationed in northeastern Syria, working with the Kurdish-led Syrian Democratic Forces to fight the Islamic State group. The U.S. carries out patrols in the region, but it was not immediately clear why the convoy drove into a government-controlled area.
In February, a Syrian was killed and another was wounded when government supporters attacked U.S. troops and tried to block their way as their convoy drove through an army checkpoint in northeastern Syria, prompting a rare clash.