US President George W Bush has said US success in Iraq will merit the sacrifice of the 4,000 troops who have died there since the Iraqi invasion began five years ago.
His comments days after the fifth anniversary of the US-led invasion.
Mr Bush insisted the decline in violence showed his strategy is working and needs more time.
His position is backed by the Republican presidential hopeful, Senator John McCain, a former Vietnam prisoner of war.
Both Democratic presidential hopefuls, Barack Obama and Hillary Clinton, have promised a quick withdrawal of US troops if elected.
The death toll of US soldiers in the conflict hit 4,000 after four troops were killed late yesterday in a Baghdad bombing.
The four died when their vehicle was hit by a roadside bomb while on patrol in southern Baghdad.
The conflict, which is now in its sixth year, has also wounded more than 29,000 US soldiers.
At least 97% of the deaths occurred after Mr Bush announced the end of ‘major combat’ in Iraq on 1 May 2003, as the military became caught between an anti-US insurgency and sectarian strife.
Despite the losses, Mr Bush has defended his decision to invade Iraq, vowing no retreat as he promised US soldiers would triumph despite the ‘high cost in lives and treasure’.
According to a tracking website, 81.3% of the US soldiers killed have died in attacks by al-Qaeda, Sunni insurgent groups loyal to Saddam Hussein and radical Shia militias.
The remainder died in non-combat related incidents.
Roadside bombs caused most of the casualties (about 40%), with small arms fire the second biggest killer.
No agreement on Iraq casualties
But up to three times as many Iraqi soldiers have died - and the number of civilians killed runs into tens and probably hundreds of thousands.
The icasualties.org website, based only on published reports, shows that around 8,000 members of the Iraqi security forces have died since the March 2003 invasion. Last year, however, the Iraqi government put the figure at 12,000.
There is no agreement when it comes to civilian casualties, particularly as many deaths are never reported in the media.
In January, a joint UN World Health Organisation and Iraqi government study concluded that between 104,000 and 223,000 Iraqis had died violently since the invasion.
As of 24 March, the independent Iraq Body Count website, based solely on incidents reported by the media, spoke of close to 90,000 deaths, of whom over a quarter died in 2007.
At the high end of the scale, British polling institute Opinion Research Business in a January report estimated the total number of civilian deaths at between 946,000 and 1.12m.
