Noting a "quiet surge" is taking place in Afghanistan, President Bush on Tuesday redirected a Marine battalion destined for Iraq to instead deploy to the Central Asian nation.

The president said he also plans to order 8,000 more combat and support troops out of Iraq by February, but plans to keep the bulk of U.S. force strength in Iraq intact until the next president takes over. No more combat brigades will come home from Iraq for the rest of this year.

Bush said the battalion, roughly 1,000 Marines, now headed to Afghanistan in November will be followed in January by an Army combat brigade. A brigade is 3,500-4,000 troops.

Bush said the U.S. and its coalition partners serving under the NATO umbrella have responded to an uptick in violence in Afghanistan by sending thousands more troops. He said in the past year, the United Kingdom, France, Poland, Bulgaria, Romania, Australia, Germany, Denmark, the Czech Republic and others have sent additional forces to Afghanistan.

"These troop increases represent a 'quiet surge' in Afghanistan. In all, the number of American troops in the country increased from less than 21,000 two years ago to nearly 31,000 today. The number of coalition troops — including NATO troops — increased from about 20,000 to about 31,000. And the number of trained Afghan army and police forces increased from less than 67,000 to nearly 144,000," he said.

Bush said the mission of the forces headed to Afghanistan will be to work with "Afghan forces to provide security for the Afghan people, protect Afghanistan's infrastructure and democratic institutions and help insure access to services like education and health care.

"They will show the citizens of Afghanistan that the government and its partners will stand with them in the battle against the Taliban and extremists," the president said in a speech at the National Defense University.

The move answers in part calls from Democrats to shift troops out of Iraq to a more sizable force in Afghanistan. Still, Democrats quickly shot back that Bush isn't doing enough to get troops out of Iraq, and into Afghanistan, where violence is rising.

"The president's plan to reduce force levels in Iraq may seem to signal movement in the right direction, but it really defers troop reductions until the next administration," said House Armed Services Committee Chairman Ike Skelton, D-Mo. "More significant troop reductions in Iraq are needed so that we can start to rebuild U.S. military readiness and provide the additional forces needed to finish the fight in Afghanistan."

Said Senate Majority Leader Harry Reid: "I am stunned that President Bush has decided to bring so few troops home from Iraq and send so few resources to Afghanistan."

About 146,000 U.S. troops will remain in Iraq. Democratic presidential nominee Barack Obama said that the 4 to 1 ratio of troops in Iraq to Afghanistan shows a misguided plan for addressing the challenges.

Bush's "plan comes up short," Obama said. "It is not enough troops, and not enough resources, with not enough urgency.

"I am convinced that it is time to change our foreign policy," he said, noting that he will withdraw troops from Iraq and create a "comprehensive strategy to finish the job in Afghanistan."

Bush said more troops may be withdrawn from Iraq in the first half of 2009 if conditions improve, but that decision will left to his successor. Bush leaves office Jan. 20.

"Here is the bottom line: While the enemy in Iraq is still dangerous, we have seized the offensive, Iraqi forces are becoming increasingly capable of leading and winning the fight," Bush said.

The president described how the surge had enabled Iraq to reduce violence, improve governance and return normalcy of life.

His military commanders say the security improvements in the country are becoming more durable, yet still fragile, and that is reason to pursue the cautious approach of keeping most U.S. forces in country.

In his upbeat account of the war, the president shared credit all around. "The progress in Iraq is a credit to the valor of American troops and civilians, the valor of Iraqi forces and the valor of our coalition partners," he said.

During his remarks, Bush also said he called the newly elected leader of Pakistan, Asif Ali Zardari, the widower of assassinated former Pakistani leader Benazir Bhutto, and pledged U.S. support "as Pakistan takes the fight to terrorists and extremists in the border regions."

The Associated Press contributed to this report.