A landmark NATO summit in Chicago endorsed an exit strategy that calls for handing control of Afghanistan to its own security forces by the middle of next year but left questions unanswered about how to prevent a slide into chaos and a Taliban resurgence after allied troops are gone.
The two-day meeting of the 28-nation military bloc marked a major milestone in a war sparked by the Sept. 11 attacks that has spanned three U.S. presidential terms and even outlasted al Qaeda leader Osama bin Laden.
Obama and NATO partners sought to show their war-weary voters the end is in sight in Afghanistan - a conflict that has strained Western budgets as well as patience - while at the same time trying to reassure Afghans that they will not be abandoned.
"We are now unified behind a plan to responsibly wind down the war in Afghanistan," Obama told the summit's closing news conference.
"Are there risks involved? Absolutely," Obama conceded, saying the Taliban remained a "robust enemy" and NATO's gains on the ground were fragile. But he insisted the overall strategy, which offered few specifics on the pace of withdrawal, was sound.
Even in NATO's outward show of solidarity, it was clear that differences remained after nearly 11 years of military engagement that has failed to defeat Taliban Islamists.
Alliance leaders acquiesced to new French President Francois Hollande's insistence on sticking to his campaign pledge to withdraw France's 3,400 troops by Dec. 31, two years ahead of NATO's timetable. While there was no sign this would send others rushing for the exits, leaders could face pressures at home.
But despite a face-to-face encounter with Pakistan's president, Obama failed to resolve a dispute overhanging the summit - Islamabad's refusal to reopen supply routes to NATO in Afghanistan seen as vital to an orderly withdrawal.
The summit's final communique ratified plans for the NATO-led army to hand over command of all combat missions to Afghan forces by the middle of 2013 and for the withdrawal of most of the 130,000 foreign troops by the end of the following year.
The statement deemed it an "irreversible" transition to full security responsibility for fledgling Afghan troops, and said NATO's mission in 2014 would shift to a training and advisory role. "This will not be a combat mission," it said.
Doubts remain, however, whether Afghan forces can stand up against a still-potent Taliban insurgency and whether President Hamid Karzai's government, widely criticized for rampant corruption, will be up to the task.
Obama, who has narrowed his goals in Afghanistan since taking office, said: "We can achieve a stable Afghanistan that won't be perfect ... and we can begin rebuilding America."
With an eye to the November presidential election, Obama has made ending the Iraq war and winding down the Afghan war a campaign theme his aides hope will help ease voter anguish over a slow U.S. economic recovery and stubbornly high unemployment.
For NATO as a whole, the long, messy Afghan conflict seems to have created its own "Vietnam Syndrome," causing it to shy away from deep on-the-ground engagement in faraway places. NATO already limited itself to an air assault in Libya last year, and has shown no stomach for military intervention in Syria.
'Graveyard of empries'
The NATO plan offered no guarantees on the future of Afghanistan, known over the centuries as the "graveyard of empires" for its ill treatment of foreign armies.
While Obama insisted Afghanistan should never again be used to plot attacks on other nations, a senior British official said: "It is unrealistic to assume that Afghanistan is going to be completely secure and there is no possibility of a terrorist threat re-emerging."
Underscoring the prospects that other allies may be tempted to follow France's lead and depart early, New Zealand announced on Monday it would pull out its 140 troops in 2013, a year ahead of schedule, saying their work was done.
Amid a growing sense of finality surrounding the NATO mission, veteran diplomatic trouble-shooter Ryan Crocker will soon step down as Obama's envoy to Afghanistan. He could leave as early as this month, sources familiar with the matter said.
At the summit's end, Obama spoke of "diligent progress" but no breakthrough with Pakistani President Asif Ali Zardari on the supply lines issue after they talked briefly on the sidelines.
Frustrated NATO officials have also been trying to persuade Pakistan to reopen its territory to NATO supplies, which Islamabad has blocked since NATO forces killed 24 Pakistani soldiers in a cross-border incident last year..
Sherry Rehman, Pakistan's ambassador to the United States, said that Zardari's presence at the summit was a positive sign. "What this conference does is acknowledge Pakistan's role," she told reporters. "Both countries I think are now seeking to bridge the differences."
With Europe's debt crisis hanging over the summit and many member-governments limited by austerity budgets, Obama also struggled to pin down final commitments from allies for the $4.1 billion a year needed to support Afghan security forces.
The funding - which will undergird Afghan's capacity to fight the Taliban and is considered vital to a smooth NATO departure - was not thought to have been fully realized at the summit. But alliance officials believe it will eventually be provided.
NATO diplomats said thinking had moved to the logistical challenge of getting a large multinational army out of the Afghan mountains and deserts and back home safely.
As Zardari, an uneasy US partner, sat with other leaders around a circular table, Obama pointedly thanked Afghanistan's neighbors who have allowed expanded shipments of war supplies since Pakistan closed off ground routes to NATO truck convoys.
NATO is seeking to compensate in the meantime with a framework agreement with Afghanistan's northern neighbor, Uzbekistan, to allow "reverse transit" of NATO supplies from Afghanistan.
Friction remains between NATO and Pakistan over Taliban guerrillas who are still finding sanctuary in Pakistan, in spite of Islamabad's professed support for the alliance's mission.
Long-term funding for the Afghan police and army, which has steadily improved its performance but is still plagued by problems, was also a focus of the summit.
The United States is unwilling to foot the entire annual bill to maintain the forces after 2014 and has been seeking pledges from allies of $1.3 billion, despite austerity measures brought on by Europe's financial crisis.
Many of the leaders in Chicago came directly from a Camp David summit of the Group of Eight wealthy nations that vowed to take all necessary measures to contain the euro-zone contagion.
Afghan funding commitments so far include $100 million annually from Britain, $120 million from Italy, $110 million from Canada, $100 million from Australia and $20 million from Turkey. Zardari told a NATO partners meeting Pakistan would also contribute $20 million.
Obama has sought to dispel Americans' concerns that shaky allies will leave US troops to finish the fight alone.
Despite pressure from some NATO members to reconsider, Hollande vowed to hold to his election pledge withdraw French troops by the year's end but said France would keep some trainers in the country for Afghan soldiers and police.
A French defense official said the United States appeared to be asking France for more financing to offset Paris' decision to exit early. "The Americans are asking for between $200-$250 million," the official said. "It's a way of compensating."