ABC

Defense Secretary Leon Panetta dismissed presumptive Republican presidential nominee Mitt Romney's criticism of President Obama's Afghanistan strategy, saying it is appropriate for the U.S. to set a date certain for ending military operations in the country at the end of 2014.

At a campaign event on Feb. 1, Romney called out Panetta for outlining plans for withdrawing forces from Afghanistan, where the U.S. has fought since 2001.

"You just scratch your head and say how can you be so misguided? And so naïve?" Romney said of Obama's Afghanistan strategy. "His secretary of defense said that on a date certain … we're going to pull out our combat troops from Afghanistan… Why in the world do you go to the people that you're fighting with and tell them the day you're pulling out your troops?"

But in a "This Week" interview, Panetta countered that the timeline has been the long-time plan first put in motion under President Bush, and confirmed by President Obama and NATO leaders at a summit in Chicago last week.

"I think you've got 50 nations in NATO that agree to a plan in Afghanistan," Panetta told me on "This Week." "It's to take us to a point where we draw down by the end of 2014… That is the plan that has been agreed to. And it's a plan that is working."

"And very frankly, the only way to get this accomplished in terms of the transition that we have to go through is to be able to set the kind of timelines that have been set here in order to ensure that we fulfill the mission of an Afghanistan that governs and secures itself," Panetta added.

While the U.S. has worked to transition control of security to Afghan forces, concerns remain that the Taliban may be able to re-assert control over the country after U.S. and NATO forces withdraw.

But Panetta said the U.S. is making progress, and will maintain "an enduring presence" in the country, aiding in counter-terrorism and training efforts beyond 2014 in order to combat the return of the Taliban or al Qaeda.

"The world needs to know that we still have a fight on our hands," Panetta said. "We're still dealing with the Taliban. Although they've been weakened, they are resilient… But we're on the right track."

And on this Memorial Day weekend, Panetta said it was important to "get the mission accomplished" in Afghanistan to honor the service members who have died there.

"I think all of us have to be constantly vigilant that whatever battle we engage in, that we not only achieve the mission but we make damn sure that we do everything possible to ensure that every life was lost for a cause that we still commit ourselves to," Panetta said.