A roadside bomb struck a U.S. convoy in western Iraq, killing three Americans, including a senior State Department official, U.S. officials said Tuesday.

The blast killed Terence Barnich, the deputy director of the State Department's Iraq Transition Assistance Office in Baghdad, as well as a U.S. soldier and a civilian contractor as their convoy left a construction site near Fallujah on Monday, military and government officials said. Two others were wounded.

Insurgents once held sway over the western province of Anbar, which was the scene of some of the deadliest fighting of the war. But violence fell off dramatically after Sunni fighters turned on Al Qaeda in Iraq and joined U.S. forces in what has become known in Iraq as "the Awakening."

Insurgents, though, have continued to sporadically target American and Iraqi security forces in Fallujah, where four employees of the Blackwater security firm were ambushed in 2004 by insurgents and their remains strung from a bridge.

The U.S. military withdrew last year from most of the cities in the vast Anbar province, including Fallujah, well before a June 30 deadline for U.S. troops to leave Iraq's urban areas.

President Barack Obama has announced the withdrawal of U.S. combat troops from Iraq by Aug. 31, 2010, leaving 30,000 to 50,000 troops as advisers and trainers. Under an Iraqi-U.S. security pact, the remaining troops must leave by the end of 2011.

The contractor killed in Monday's blast was a Defense Department employee assigned to the U.S. Embassy in Baghdad, U.S. officials said. His name and that of the soldier killed have not been released pending notification of next of kin.

Barnich, 56, of Chicago, and the others were returning from an inspection of a U.S. government-funded wastewater treatment plant under construction in Fallujah when their vehicle drove over a roadside bomb, said State Department spokesman Robert Wood.

Like many cities in Iraq, Fallujah has a number of U.S.-supported reconstruction projects, many of them aimed at improving essential services and promoting businesses.

American military and government officials see the projects as essential to helping maintain security gains. Some of the projects are overseen by provisional reconstruction teams and a joint U.S. civil-military office. Others are directed by the State Department's U.S. Agency for International Development.

Barnich and the others were working with local Iraqi authorities on the wastewater project, which is the largest of its kind ever undertaken in Iraq, Wood said.

"The goal is to bring help to the people in war-torn Anbar province," Wood said.

Barnich was hired in 2007 as deputy director of the Iraq Transition Assistance Office in Baghdad. He also served as the former chairman of the Illinois Commerce Commission, Wood said.

Barnich originally planned to work in Iraq only 11 months, but he loved the work, Craig Clausen, a colleague of Barnich, told The Associated Press. He said Barnich had been expected to return to his job as CEO of the Chicago-based consulting firm New Paradigm Resources Group in July.

At least five other State Department employees have been killed in Iraq, including Steven Farley, who died in a June 2008 bombing at an Iraqi council building in Baghdad's Sadr City.

As of Monday, at least 4,301 members of the U.S. military had died in the Iraq war since it began in March 2003, according to an Associated Press count.