A grim milestone was passed in Iraq today when a US Marine was killed in action south of Baghdad - the 1,500th American soldier to lose his life since the invasion.

The US military said the soldier, assigned to the 1st Marine Expeditionary Force, was killed "while conducting security and stability operations".

It would not give any more details, saying in a statement: "Force protection measures preclude the release of any information that could aid enemy personnel in assessing the effectiveness, or lack thereof, with regard to their tactics, techniques and procedures. The release of more details about the incident could place our personnel at greater risk."

The soldier will not be named until his next of kin is informed.

According to an Associated Press count, the death of the Marine brought the US military toll to exactly 1,500 since the US-led invasion on March 20, 2003, almost two years ago. A total of 86 UK soldiers have died in Iraq during the same period.

Iraqbodycount.net, an independent website which relies on credible media reports of deaths, puts the number of Iraqi civilians killed since the invasion at up to 18,395 - although it says many other deaths may have gone unreported. A statistical study in the medical journal the Lancet estimated that Iraqi civilian deaths could be as high as 198,000.

Worryingly, the number of military deaths has shown no sign of falling since President Bush landed on USS Abraham Lincoln on May 1, 2003 with a banner saying "Mission Accomplished" and declared an end to major combat operations.

A total of 107 US military personnel were killed in Iraq in January, including 31 in a still unexplained helicopter crash in the western desert near Jordan that was the single most costly incident for US forces since the invasion. Ninety per cent of all coalition deaths have come since the US command celebrated the fall of Baghdad.

Experts say the death toll from Iraq is still minor compared to that of the war in Vietnam, the greatest blunder in US military history, where the death of 58,000 Americans instilled a generational fear of 'body bags' in Pentagon planners.

But the losses in Iraq signally failed to derail President Bush's re-election last November, although it has helped to polarise American voters over the issue of Iraq.

Ted Carpenter, a defence analyst at Washington's Cato Institute, said that a more useful comparison might be made with Soviet losses in Afghanistan in the 1980s - another situation that pitted an invading superpower against a tenacious Muslim insurgency.

About 15,000 Soviet troops were killed during nine years of fighting after the Soviet invasion of Afghanistan in December 1979, a monthly total about twice as high as that suffered by the more highly trained US forces in Iraq.

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