President George W. Bush is saddened by the loss of 4,000 U.S. troops in Iraq and will focus on ensuring the U.S. succeeds in the 5-year-old conflict, the White House said on Monday.

"It's a sober moment, and one that all of us can focus on in terms of the number of 4,000," White House spokeswoman Dana Perino said after a roadside bomb in Iraq killed four U.S. soldiers, pushing the U.S. death toll to a new milestone.

"The president feels each and every one of the deaths very strongly and he grieves for their families," Perino said. "He obviously is grieved by the moment but he mourns the loss of every single life."

The 4,000th U.S. death came days after Bush marked the fifth anniversary of the war and said the United States was on track toward victory.

He cited the "embarrassing situation and public perception of differences between my views and administration policy" as the reason for retiring.

An article by Esquire magazine said he was opposed to the use of force against Iran over its nuclear activities.

Adm Fallon said he did not believe there were differences over policy objectives.

The 63-year-old admiral became head of the US Central Command - which covers an area from the Horn of Africa into central Asia and includes responsibility for US operations in Iraq and Afghanistan - a year ago.

He said "there is a misperception" that the admiral disagreed with the Bush administration's policies towards Iran. "I don't think there were differences at all," Mr Gates said.

A statement released by Adm Fallon through Central Command's Florida headquarters seemed to reflect those sentiments.

"I don't believe there have ever been any differences about the objectives of our policy in the Central Command," he said.

"The simple perception that there is makes it difficult for me to effectively serve America's interests there."

A suicide bomber killed five American soldiers on a foot patrol Monday after detonating his explosives vest in central Baghdad, the U.S. military said.

It was the deadliest attack on American forces in Iraq since a Jan. 28 roadside bombing and ambush killed five soldiers in Mosul in northern Iraq.

Military spokesman Maj. Mark Cheedle said that "it was reported to us as a suicide bomber."

With nearly 100% of the ballots counted, the election commission has announced he won 70.23% of the vote.

Mr Medvedev said he hoped to work in an "effective tandem" with Mr Putin as his prime minister.

As president, he said, he would control foreign policy with the defence of Russian interests his chief priority.

Mr Putin, he confirmed, would be moving out of the Kremlin.

Mr Medvedev's nearest rival was Communist leader Gennady Zyuganov, with 17.76% of the vote. He vowed to go to court over alleged fraud, Itar-Tass news agency reports.