A Syrian official said four men who tried to storm the embassy were killed.
Witnesses said at least one Syrian guard was killed and a Syrian official told Reuters all U.S. diplomats were safe.
The embassy is in the Rawda area which also houses vital security installations, the houses of senior Syrian officials and other embassies.
The witnesses said Syrian security forces surrounded the embassy building and sealed off the area.
Britain's ambassador to Syria Peter Ford told CNN that the attack did not appear to be a "major al-Qaeda like operation, but an operation by a small group".
The U.S. State Department in Washington said it was checking the reports and had no immediate information.
Thanks Got a right to Life? . . Huh?