BAGHDAD (AFP) — 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.

The four soldiers died when their vehicle was hit by a roadside bomb while on patrol late Sunday in southern Baghdad, bringing the overall toll to 4,000, according to an AFP tally based on independent website.

Another soldier was wounded in the attack, a military statement said.

The chaotic and brutal conflict which is now in its sixth year has also wounded more than 29,000 American soldiers, according to icasualties.org.

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At least 97 percent of the deaths occurred after US President George W. Bush announced the end of "major combat" in Iraq on May 1, 2003, as the military became caught between a raging anti-American insurgency and brutal sectarian strife unleashed since the toppling of Saddam.

140 American servicemembers died before May 1, 2003, out of a total 4,000.

Despite the losses, Bush on the eve of the war's fifth anniversary defended his decision to invade Iraq, vowing no retreat as he promised American soldiers would triumph despite the "high cost in lives and treasure."

US military spokesman in Baghdad, Rear Admiral Gregory Smith, said the loss of every soldier was "tragic".

"No casualty is more or less significant than another; each soldier, marine, airman and sailor is equally precious and their loss equally tragic," Smith told AFP.

"Being in the military means we are willingly in harm's way to protect others in order to bring hope and a sustainable security to the Iraqi people."

According to icasualties.org, 81.3 percent of the soldiers killed have died in attacks by Al-Qaeda in Iraq fighters, Sunni insurgent groups loyal to Saddam and radical Shiite militias.

The remainder died in non-combat related incidents.

Roadside bombs caused most of the casualties, with small arms fire the second biggest killer.

Around 40 percent of those killed were struck by roadside bombs, according to the website, making these weapons the main cause of fatalities.

Others died variously in car bombings, small arms fire, helicopter crashes, ambushes, rocket attacks and suicide bombings.

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