WASHINGTON (CNN) -- U.S. President George W. Bush on Tuesday announced a plan to withdraw about 8,000 U.S. troops from Iraq by February and to beef up the U.S. military presence in Afghanistan.
President Bush said Tuesday that he will soon start bringing some U.S. troops home from Iraq.
Bush said in a speech on Tuesday morning 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.
The troop cut -- smaller than many had expected due to a desire not to jeopardize recent security gains made in Iraq -- will mark one of Bush's final decisions on a war that has defined his presidency.
Speaking at the National Defense University in Washington, Bush said he is making the move based on a recommendation from top military officers, including Gen. David Petraeus, the highest-ranking U.S. military officer in Baghdad. Watch Bush announce troop reduction in Iraq »
"He and the Joint Chiefs of Staff have recommended that we move forward with additional force reductions," the president said.
"Over the next several months, we will bring home about 3,400 combat support forces -- including aviation personnel, explosive ordnance teams, combat and construction engineers, military police, and logistical support forces. By November, we will bring home a Marine battalion that is now serving in Anbar province. And in February of 2009, another Army combat brigade will come home.
"This amounts to about 8,000 additional American troops returning home without replacement. And if the progress in Iraq continues to hold, Gen. Petraeus and our military leaders believe additional reductions will be possible in the first half of 2009."
Read Bush's complete speech about troop reduction
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Bush cited what he said has been a reduction of violence in Iraq to its lowest point since spring 2004.
"Civilian deaths are down, sectarian killings are down, suicide bombings are down and normal life is returning to communities across the country," he said.
Though progress "is still fragile and reversible," he said, Petraeus and U.S. Ambassador to Iraq Ryan Crocker "report that there now appears to be a 'degree of durability' to the gains we have made."
"While the enemy in Iraq is still dangerous, we have seized the offensive, and Iraqi forces are becoming increasingly capable of leading and winning the fight," he added. "As a result, we have been able to carry out a policy of 'return on success' -- reducing American combat forces in Iraq as conditions on the ground continue to improve."
But Bush 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 today.
In November, a Marine battalion that had been poised to be sent to Iraq will instead be sent to Afghanistan and an Army combat brigade of several thousand fighters will go to Afghanistan in January, he said.
"They will help clarify a stark contrast in Afghanistan: While the terrorists and extremists deliberately target and murder the innocent, coalition and Afghan forces risk their lives to protect the innocent," he said.
But the president acknowledged the U.S. military is sometimes responsible for civilian deaths, which Afghanistan President Hamid Karzai has complained bitterly about.
"Regrettably, there will be times when our pursuit of the enemy will result in accidental civilian deaths," Bush said. "I have given President Karzai my word that America will work closely with the Afghan government to ensure the security of the Afghan people while protecting innocent life."
One analyst on Iraqi affairs said the plan announced Tuesday reflected concerns of commanders that any rush to force troop reductions could lead to instability.
"This plan does, however, mean continuing stress on both the active and reserve forces," Anthony Cordesman, an Iraq expert at the Center for Strategic and International Studies, told The Associated Press.
Democratic presidential candidate Barack Obama wants all U.S. forces out of Iraq within 16 months of taking office while his Republican opponent, John McCain, says he would rely on U.S. military commanders to advise on the timing and pace of any troop reductions.