It was the biggest Jordanian anti-US gathering since President Barack Obama threatened a "limited" strike on Syrian targets in response to an alleged August 21 chemical attack blamed on Bashar Assad's regime. A similar protest last week drew only a couple of dozen activists.
Today's protest was planned by youth movements affiliated with Marxist and leftist groups, which are usually fiery critics of Washington because they regard its Mideast policy as biased in favor of Israel.
The demonstrators drew parallels between Obama and former US President George W Bush, calling both "warmongers."