The United States is "very committed" to begin troops drawdown in Afghanistan in July 2011, but large number of soldiers will remain, Chairman of the Joint Chiefs of Staff Mike Mullen said on a televised interview broadcast Sunday.

"We will start drawing down troops next July," Mullen told CNN' s news program GPS, stressing any drawdown will be based on conditions on the ground and via a recommendation from commanders on the ground.

"We're very committed to beginning the drawdown," Mullen said. "But there will continue to be a large number of U.S. and allied troops on the ground in Afghanistan after July 2011."

Mullen said it is too soon to know the number of troops and locations the drawdown will affect.

In ordering the deployment of 30,000 new troops to Afghanistan, U.S. President Barack Obama late last year set July 2011 as the time to begin the drawdown. The newly deployed troops didn't make much progress in Afghanistan. A Pentagon report submitted to Congress last week found progress across Afghanistan "uneven," with only modest gains in security, governance and development in key areas.

NATO, which heads the mission in Afghanistan, has set 2014 as a goal to complete the security handover to Afghan forces.