Six other U.S. soldiers were meanwhile reported to have been among some 350 people who were made ill when three suicide bombers exploded vehicles rigged with tanks of toxic chlorine gas on March 16 in Anbar Province. Up to eight people were reported killed in those attacks.
March 20 will be the fourth anniversary of the start of the war.
No Australian Withdrawal
Meanwhile, Australian Prime Minister John Howard says Australian troops will remain in Iraq until Iraqis are able to take control of security duties.
Howard, speaking on March 17 on a visit to Baghdad, refused to say when Australia's 1,400 troops might withdraw from Iraq.
Iraqi Prime Minister Nuri al-Maliki said his government wants Australia to remain in Iraq until all terrorist activities cease.
Howard arrived in Baghdad after his plane was forced to make an emergency landing in southern Iraq after the aircraft filled with smoke and fumes, forcing Howard and others to put on gas masks.
Howard was not hurt. The cause of the incident is under investigation.
Thousands of people have taken part in protests against the Iraq war in cities in the United States and around the world.
Thousands participated in an antiwar march in the U.S. capital, Washington, while smaller demonstrations were held in Los Angeles, San Francisco, and other cities.
About 2,000 anti-war demonstrators marched through Tokyo today carrying banners that read "Stop Bush's war." A demonstration outside the U.S. Embassy in Malaysia today drew some 200 people who read antiwar speeches and held banners opposing the war in Iraq.
Protests also took place in a number of European capitals, as well as in Turkey and Australia.
(compiled from agency reports)