WASHINGTON (CNN) -- President Bush announced Wednesday that Defense Secretary Donald Rumsfeld is stepping down from his post.

"The timing is right for new leadership at the Pentagon," Bush said at the White House Wednesday afternoon.

Rumsfeld has been heavily criticized for his policies in Iraq, and exit polls taken during Tuesday's midterm election showed strong voter dissatisfaction -- 57 percent -- with the Iraq war.

"I recognize that many Americans voted last night to register their displeasure with the lack of progress being made" in Iraq, Bush said...

Bush said he has "a series of thoughtful conversations" with Rumsfeld about the defense secretary's resignation.

Former CIA chief Robert Gates,who headed that agency from 1991 until 1993, will be nominated to take over as defense secretary, Bush said Wednesday.

Gates is now president of Texas A&M University in College Station, Texas...