The U.S. military has announced the death of the 2,000th American service member to perish in the Iraqi campaign, but a spokesman tried to downplay the benchmark, calling it "artificial."

"The 2,000 service members killed in Iraq supporting Operation Iraqi Freedom is not a milestone," U.S. army Lt.-Col. Steve Boylan wrote in an e-mail to reporters, according to the Associated Press.

"It is an artificial mark on the wall set by individuals or groups with specific agendas and ulterior motives," Boylan said, before the Pentagon issued a statement on Tuesday saying that army Staff Sgt. George Alexander had died in Texas on the weekend.

People protest the war in Iraq on a downtown corner in Nashville, Tenn. Demonstrators gathered during rush hour after news came out that the U.S. death toll for the war in Iraq reached 2,000. (AP Photo/Mark Humphrey)

U.S. President George W. Bush – who has faced flagging support for the campaign – also warned in the day that the country should brace for more casualties before it finishes its work in Iraq.

The U.S. military doesn't release a running tally of deaths in American units assigned to the Iraq campaign, in Iraq, Kuwait or elsewhere.

However, Alexander's death brings the total to 2,000, according to an unofficial count by CBC News.

More than 15,000 American military personnel have been wounded in the campaign.

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Alexander, 34, was based at Fort Benning, Ga., and assigned to the 1st Batallion, 15th Infantry Regiment, 3rd Brigade.

He was injured when a bomb exploded near his vehicle in the city of Samarra, north of Baghdad, on Oct. 17.

Earlier Tuesday, Bush told military spouses at Bolling Air Force Base in Washington that completing the Iraq mission would be the best way to pay tribute to the dead.

"The terrorists are as brutal an enemy as we have ever faced, unconstrained by any notion of common humanity and by the rules of warfare," he said.

"No one should underestimate the difficulties ahead."