WASHINGTON —  President Bush is expected to nominate Marine Gen. Peter Pace to serve a second two-year term as chairman of the Joint Chiefs of Staff, maintaining Pace's leadership during the increasingly unpopular Iraq war.

The move would keep Pace as one of the nation's top two military leaders for eight years — longer than anyone else has served as chairman and vice chairman of the joint staff, since the top job was first filled in 1949.

A senior defense official, who requested anonymity because the announcement had not yet been made, said it was not clear when the decision would be made public. Pace's renomination requires at least two waivers. One is because he will have served more than six years as either the chairman or vice chairman of the joint staff, and the second would allow him to continue to serve on active duty beyond the age of 62. The Vietnam War veteran will turn 62 in November.

Although Pace has held a top leadership position during the entire length of the Iraq and Afghanistan conflicts, he has largely escaped the harsh criticism faced by other architects of the war. Former Defense Secretary Donald Rumsfeld stepped down late last year after a watershed anti-war election vote gave control of the House and Senate to the Democrats.

And more recently, the cadre of U.S. military commanders in the Middle East has turned over — giving the administration a fresh group of leaders to map out how to extricate U.S. troops from Iraq without leaving the fledgling democracy in chaos.