By Barbara Starr and Adam Levine, with reporting by Rachel Burstein and Larry Shaughnessy

The United States and NATO want to end their combat mission in Afghanistan next year, transitioning primarily to a training role in which Afghan security forces will take the lead, Defense Secretary Leon Panetta said Wednesday.

"Our goal is to complete all of that transition in 2013 and then, hopefully, by mid- to the latter part of 2013, we'll be able to make a transition from a combat role to a training, advise and assist role," he told reporters traveling with him to Brussels, according to a transcript released by the Pentagon. The result will be that "2014 then becomes a year of consolidating the transition and making sure that those gains are in fact held, so that we can move towards a more enduring presence beyond 2014."

That enduring presence will include "a large civilian presence" involved with development, he continued.

Under Panetta's scenario, the transition would come a year before the 2014 deadline to end the war in Afghanistan that had been set by the Obama administration.

A U.S. administration official stressed that the transition is 2013 is the hope, but "nothing is final" until leaders of the NATO countries convene in Chicago this May.

In a statement, Rep. Adam Smith, ranking member of the House Armed Service Committee, called Panetta's timeline "a reasonable goal."

But the committee chairman, Rep. Howard P. "Buck" McKeon, said it was too early to make such predictions. "Announcing a change in mission in Afghanistan - before we have even validated the Afghan Security Forces can maintain stability in the areas we have already transitioned and ahead of the fighting season - is premature," he said.

"Our goal is to complete all of that transition in 2013 and then, hopefully, by mid- to the latter part of 2013, we'll be able to make - you know, to make a transition from a combat role to a training, advise and assist role, which is basically fulfilling what Lisbon was all about," the administration official said in an email.

Late last year, Gen. John Allen, the commander of U.S. and NATO forces in Afghanistan, said U.S. forces will begin to be deployed this year within Afghan units as advisers and trainers, reducing the direct combat role of foreign troops in the country.

Afghanistan's security force exceeds 305,000 and is headed toward 352,000 this year. At the same time, the United States will be withdrawing forces throughout 2012, with the goal of reducing U.S. troop strength to 68,000 by year's end from more than 100,000. There will also be 38,000 troops from other NATO countries.

The U.S. goal is for Afghan forces, advised by Americans, to take the lead.

"That will, in many respects, be a preview of how we'll see our forces postured in the years to come," Allen said in December. "The crossover point where we become largely an advisory, assisting and education force versus a force that is engaged at any given moment in counterinsurgency, that crossover point remains to be determined."

The United States will still maintain its commitment to transition to an Afghan lead by the end of 2014, according to Pentagon spokesman Capt. John Kirby.

"Nothing has changed about the strategy our troops are executing: We are working to prevent Afghanistan from ever again becoming a safe haven for al Qaeda and its allies," Kirby said in a statement. "Nothing has changed about the goal of developing strong and capable Afghan security forces."

The news comes a few days after France announced that it will withdraw its troops a year earlier than 2014. That announcement came after four of its troops were killed by an Afghan soldier.

The Obama administration has taken pains to to show that the alliance is still strong and committed to the 2014 deadline.

"The end of this process, the end of this transition, the end of this drawdown in which the Afghans fully move into the lead, is slated to be 2014," White House deputy national security adviser Ben Rhodes said in Chicago on Tuesday. "Just as we made decisions about the pace of our drawdown, other nations will make decisions."

NATO will meet in May in Chicago to discuss the war and to ensure that the 28-member alliance is "aligned on our drawdowns and transition," Rhodes said.

But there are significant questions as to whether the NATO and Afghanistan can sufficiently weaken the Taliban or bring them to the negotiating table.

A leaked NATO report underscores concerns about Pakistan's support of the Taliban. The document revives the longstanding accusation that elements in Pakistan's Inter Services Intelligence agency are aiding the insurgency in Afghanistan.

It says the ISI knows the whereabouts of all senior Taliban commanders, according to a Times of London journalist who has read the classified NATO document.

The Obama administration is trying to get the Taliban to negotiate and has proposed a transfer of some prisoners from Guantanamo to Qatar as a sign of good faith by the United States. The administration said any discussion about releasing the detainees would be preliminary and would hinge on the Taliban renouncing terrorism and agreeing to peace talks.

In addition to the release of Guantanamo prisoners, the Taliban would be allowed to open an office in Qatar.

But that proposed transfer is controversial. In a letter to President Obama on Wednesday, Rep. Duncan Hunter, R-California, a former Marine officer who served in Afghanistan, warned that the release would "send the wrong message to the Taliban."

"Releasing prisoners strictly for the purpose of accelerating negotiations undermines the U.S. mission in Afghanistan and deliberately ignores the threat of a Taliban resurgence," Hunter wrote.

Sen. John McCain, R-Arizona, who attended a briefing by administration officials on Tuesday night about the potential release, called it "really, really bizarre."

"This whole thing is highly questionable because the Taliban know we're leaving. They know we're leaving. Put yourself in their shoes." McCain said. "There are many people who are experts in the region who say they are rope-a-doping us."

Even as the United States plans its withdrawal, it is working on ensuring that it can continue to supply troops. The Obama administration is temporarily lifting a ban on military assistance to Uzbekistan, a Central Asian nation that plays a crucial role in providing an overland supply route for U.S. military cargo into Afghanistan.

Secretary of State Hillary Clinton signed a waiver January 18 under which the United States can provide Uzbekistan with "non-lethal" defensive equipment, State Department spokeswoman Victoria Nuland said Tuesday.