One US soldier was killed and 10 were wounded in central Baghdad on Sunday, the US military said today.
The military said two Iraqi soldiers and an interpreter were also hurt.
The death raised to 66 the number of US soldiers killed in Iraq in September, according to icasualties.org, a website that tracks US military deaths in Iraq.
That makes September the least deadly month for US troops in Iraq since August last year, when 65 soldiers were killed.
US commanders have attributed the drop in troop deaths to a rise in force levels this year and a series of large-scale offensives against al-Qaeda and other militant groups.
Yesterday, Iraqi government data showed civilian deaths from violence across Iraq had fallen 50 per cent in September from August.