Washington (CNN) -- An upcoming military review of the war in Afghanistan is not expected to result in any major changes in U.S. strategy, Joint Chiefs of Staff Chairman Adm. Mike Mullen said Sunday.
In an interview with CNN's "State of the Union" program, Mullen said the U.S.-led international force has "started to make progress" in its mission to prevent Afghanistan from becoming a safe haven for international terrorist groups.
However, Mullen described the progress so far as "fragile." He cited the training of Afghanistan forces to take over security responsibilities as an area in which progress has occurred but challenges remain.
The military review is due in December, a year after President Barack Obama ordered additional U.S. troops to Afghanistan as part of a strategy that would see some forces coming home as soon as July 2011.
Mullen lauded a weekend meeting of NATO leaders in Portugal that set a goal of ending combat operations for international forces in Afghanistan by the end of 2014. He reaffirmed Obama's statement Saturday that the United States and its allies wanted to hand over security responsibility for all of Afghanistan to that country's security forces by then, and would play a training and support role after that.
"We think that's a reasonable goal," Mullen said.
"We will still have forces to -- and I think the president said it yesterday as well -- to train and assist," Mullen said of NATO troops in Afghanistan after 2014. The plan is for all combat forces to be out that year, he said.
Mullen said the transition of security responsibility from the U.S.-led international force to Afghanistan security forces would start in the spring of 2011, and he described it as a "district by district" approach based on conditions on the ground.