The soldier was killed while conducting what the US military described as "security and stability operations", refusing to give any further details on the grounds that it could place personnel at greater risk.

On Thursday, three US marines were killed in separate incidents in the province, home to the rebel strongold of Fallujah, which US jets have pounded in recent days.

Before the latest deaths, the Pentagon reported 1,027 US military fatalities in Iraq since the March 2003 invasion.