The Obama administration is exploring a shift in the military's mission in Afghanistan to an advisory role as soon as next year, senior officials said, a move that would scale back U.S. combat duties well ahead of their scheduled conclusion at the end of 2014.
Such a move would have broad implications for the U.S. strategy in Afghanistan. It could begin a phase-out of the current troop-intensive approach, which focuses on protecting the Afghan population, in favor of a greater focus on targeted counterterrorism operations, as well as training the Afghan military.
A transition to a training mission could also allow for a faster drawdown of U.S. forces in the country, though officials said discussions about troop levels have yet to move forward.
The revised approach has been discussed in recent high-level meetings involving top defense and administration officials, according to people involved in the deliberations. No decisions have been made, officials said, and policy makers could consider other options that would adjust the mission in other ways, officials said.
Officials said agreement on a formal shift to an advisory role could come as early as a North Atlantic Treaty Organization meeting in May—in the heat of the U.S. presidential election campaign.
Some officials have drawn comparisons to President Barack Obama's 2009 decision to switch to an "advise and assist" role in Iraq and to declare a formal end to U.S. combat operations there. In Iraq, after mid-2009, troops were largely confined to their bases.
Security conditions in Afghanistan are different, however, and will likely require U.S. troops, particularly Special Operations forces, to continue to accompany their Afghan counterparts into battle after the U.S. takes an advisory role.
Defense officials said the U.S. still would be directly involved in many combat operations, though increasingly with Afghan forces in the lead.
"It's not like we're…going to move to train, advise and assist and just let the Afghans do everything on their own and we're not fighting bad guys," a senior official said.
It would be wrong, the official said, to think the U.S. was now considering "ending the war in Afghanistan earlier than expected."
Although discussions about changing the mission are in the early stages, their urgency is growing ahead of the NATO summit, to be held in Chicago, Mr. Obama's hometown.
The U.S. and its allies hope to use the summit to flesh out their withdrawal plans, U.S. officials said. At a NATO summit in Lisbon in 2010, the U.S. and its allies backed plans to hand over security responsibility to the Afghans by the end of 2014.
For Mr. Obama, the political stakes are growing. There has been a sharp decline in domestic political support for the Afghan war amid a weak economy and mounting fiscal woes. A change in the mission at the NATO summit would come at the height of the 2012 campaign, in which some of Mr. Obama's Republican challengers have called for winding down the war in Afghanistan.
When Mr. Obama came to office in January 2009, there were just over 30,000 U.S. troops in Afghanistan. He quickly added 21,000 more.
In a lengthy strategy review later that year, military leaders requested 40,000 additional troops to support a counterinsurgency campaign, a troop-intensive approach.
Vice President Joe Biden and others argued that a large troop buildup could be counterproductive, and instead advocated a campaign emphasizing strikes against Taliban and al Qaeda leaders. But Mr. Obama in December 2009 authorized a surge of 33,000 troops, which allowed commanders to step up the counterinsurgency campaign. He has said he would withdraw those surge troops by the end of next summer.
The recent discussions reflect ambivalence within the administration over whether the counterinsurgency approach was merited.
Some administration officials privately argued that it was too costly and unrealistic, compared to a counterterrorism strategy that relies more heavily on using Special Operations forces to hunt down and kill militants, rather than deploying large numbers of forces in a "hearts-and-minds" campaign.
One official described the shift being considered as a change in focus—as opposed to an end to counterinsurgency. Training local forces, defense officials noted, is part of counterinsurgency operations.
"We are doing more training and assistance right now. We are doing more and more each month.…It is the normal maturation of [the Afghans] going in the lead," a defense official said.
One of the perils of such a transition is that the Afghan security forces have long been seen as incapable of handling the security role now managed by the U.S. and its NATO partners.
But some officials say the administration now sees the goal of building a perfect Afghan force by 2014 as no longer attainable, and is looking for a force that is "good enough" to keep the Taliban from overtaking the country.
In anticipation of changes in the U.S. troop posture, the commander of NATO forces in Afghanistan, U.S. Gen. John Allen, is pushing to begin giving Afghan forces the lead in some areas of Afghanistan where the fighting is fierce. Doing so would test Afghan fighting skills before the U.S. withdrawal makes it more difficult for the U.S. to provide them with sufficient backup.
Congressional officials briefed on the discussions said Gen. Allen's accelerated transition plan would provide a test of the drawdown schedule.
"Frankly, if we're going to have fewer troops in Afghanistan in a year or two, then you might as well do it now while we have enough troops to bail them out when they screw up," one official said.
Many top military officials are reluctant to pull out quickly and want to keep as many troops on the ground and in combat in Afghanistan as long as the White House will allow it.
But some military officials have begun to question the common wisdom at the Pentagon.
These officials argue the U.S. military has been too slow to hand off the lead in combat operations to the Afghans, relying on more capable U.S. and NATO troops.
"The large number of Americans that are present right now, in a perverse way, is keeping the Afghans from being moved more rapidly into the lead of this fight," said David Barno, a former top commander in Afghanistan who just returned from a visit to the country.
The White House has yet to decide what the U.S. presence in Afghanistan will look like after 2014. Preliminary discussions include how many troops would be needed to protect the U.S. embassy and consulates around the country after the bulk of the forces withdraw.
The question confronting the administration is whether to follow the Iraq model, where Mr. Obama last month decided to fully withdraw U.S. forces, or opt to keep some troops in place to conduct counterterrorism operations alongside the Afghans longer term.