U.S. President George W. Bush has announced that he plans to withdraw about 8,000 U.S. troops from Iraq by next February and to send some 4,500 troops to Afghanistan next January.

In a speech at the National Defense University, Bush said that improving conditions in Iraq will allow a "quiet surge" of American troops to Afghanistan, where there has been a resurgence of the Taliban and a growth in violence.

He also said he is making the move based on a recommendation from top military officers, including David Petraeus, the highest-ranking U.S. military officer in Baghdad.

"General (David) Petraeus has just completed a review of the situation in Iraq - and he and the Joint Chiefs of Staff have recommended that we move forward with additional force reductions. And I agree. Over the next several months, we will bring home about 3,400 combat support forces."

Bush also said more work needs to be done in Afghanistan, where the number of U.S. forces has risen from 20,000 two years ago to 31,000 at present.