US soldiers patrol in Diyala Province, northeast of Baghdad. The death toll of US soldiers in the five-year Iraq conflict has hit 4,000 in what the US military said Monday was a "tragic" loss of lives after four troops were killed in a Baghdad bombing.(Xinhua/AFP Photo)

Despite the losses, US President George W. Bush last Wednesday defended his Iraqi policy, vowing no retreat as he promised American soldiers would triumph despite the "high cost in lives and treasure".

Hillary Clinton and Barack Obama, both vying for the Democratic presidential candidate, pledge to end the war once elected.

Yet, John McCain, who is the Republican candidate, supports Bush's stance.