Petraeus takes over as head of U.S. Central Command

Petraeus took command of Centcom and was given responsibility for overseeing the wars in Iraq and Afghanistan at a ceremony at MacDill Air Force Base near Tampa.

He was the top U.S. commander in Iraq. Now, as the top regional commander, Petraeus will continue to oversee that war, but at Centcom, his most urgent task will be helping to craft a new strategy for the war in Afghanistan.

"Under his leadership our troops have dealt our enemies in Iraq a tremendous blow," Gates said. "Now he will take aim at our adversaries in Afghanistan."

Later in the day, during a news conference aboard his plane, Gates said that Petraeus would have to find a way to weave together various ongoing military reviews of the Afghanistan war into a single strategy as well as better coordinate various reconstruction efforts.

"We've got four or five different strategies going on right now. At some point all of that has to come together and we need to have one coherent plan that everyone signs up for," Gates said.

The conflict in Afghanistan has grown more violent this year and in its closing days, the Bush administration has initiated a broad strategy review, led by the National Security Council. The Joint Chiefs of Staff also have a planning effort underway, designed in part to present options to the next administration. Petraeus is working on his own plan for Afghanistan. In addition, the North Atlantic Treaty Organization is engaged in a strategic planning effort.

For all the efforts, a crucial question concerns the number of troops needed. President Bush has announced that an additional Army brigade, about 3,500 soldiers, will head to Afghanistan early next year. But U.S. commanders in Afghanistan have said that they need as many as 20,000 more troops.

Gates said he had briefly discussed with Petraeus the appeal from commanders in Afghanistan for three additional brigades. That request has not formally been presented to Gates, but he said he had told Petraeus that he thought it was something the U.S. should "satisfy in the course of 2009."

The Pentagon chief sounded skeptical about the need for more troops beyond those brigades and said U.S. allies were unlikely to send more troops.