Four more US soldiers have been killed in Iraq, the military said today.
The latest fatalities take the US death toll for the first six days of the month to 21.
Off the battlefield, Iraq's national unity government is in crisis after five secularist ministers said they would boycott cabinet meetings until Prime Minister Nuri al-Maliki addressed demands they first gave him in February.
The move means that 17 ministers, nearly half the cabinet, have now quit or are boycotting government meetings. The main Sunni Arab bloc pulled out last week and ministers loyal to Shia cleric Moqtada al-Sadr withdrew in April.
While Mr Maliki went ahead with a planned trip to Turkey and Iran, the secular Iraqi List of former prime minister Iyad Allawi held a news conference in Baghdad to explain why they were boycotting the meetings, in which the embattled prime minister now only has a narrow working majority.
Washington is growing increasingly impatient with the lack of political progress by Iraq's deeply divided political parties towards national reconciliation.
President George W Bush has sent nearly 30,000 extra troops to help stabilise Iraq and give Mr Maliki's Shia-led government breathing space to reach a political accommodation to end the sectarian violence.