Praising the progress made by U.S. and NATO forces in Afghanistan, the general, speaking on Britain's BBC and ITV television, said: "We have to say that, militarily, the surge worked."
Dempsey, in comments he also made in a lecture, welcomed the endorsement of a proposed long-term security agreement between Afghanistan and the United States by more than 2,000 delegates at a recent loya jirga called by Afghan President Hamid Karzai.
The general said the loya jirga, an assembly of elders and leaders, helped bring together many disparate Afghan groups, the U.S. Defense Department reported on its Web site.
He said NATO and the Afghan government are making progress in getting Afghan forces ready to take over responsibility for the country's security by the end of 2014 as foreign forces withdraw.
Still, the general said, there will have to be some partnership agreement between Afghanistan and other countries beyond 2014.
"I would say that Afghanistan will still be in the balance three years from now," Dempsey said. "This is a mission, this is a challenge, this is a neighborhood that requires constant vigilance. It requires capability, capacity, communications and it requires partnership."