(CNN) - The commanding U.S. general in Afghanistan says success in the war there will require a long and steady U.S. commitment.
"We will have an enduring commitment here in some fashion," Gen. David Petraeus said in an interview broadcast Sunday on the NBC program "Meet the Press."
He later added: "I think this is going require a substantial, significant commitment and that it is going to have to be enduring to some degree."
The Obama administration has been criticized for its announced strategy to start a troop withdrawal in August 2011, with conservatives saying it signals U.S. intentions to the enemy while liberals complain it doesn't end the war soon enough.
Petraeus emphasized that the planned "transition" would be based on conditions on the ground, with troops withdrawn only from areas where Afghan security forces are in control.
He also said that he agreed to assume command in Afghanistan this summer to replace the ousted Gen. Stanley McChrystal in order to achieve success, rather than just oversee the end.
"I didn't come out here to carry out a graceful exit or something like that," Petraeus said.