But the accord appeared short on details and timelines, and US Secretary of State Hillary Rodham Clinton warned of a rocky road ahead in a country beset with a resilient insurgency, limited resources and a weak, sometimes dysfunctional central government.

Clinton said she was pleased with progress toward eliminating the shortage of allied trainers for the Afghan Army and police. She offered a generally sunny outlook for Afghanistan and said the government of President Hamid Karzai gets too little credit for progress in building a viable democracy.

“We believe that with sufficient attention, training and mentoring, the Afghans themselves are perfectly capable of defending themselves against insurgents,” she told a news conference. “Does that mean it will be smooth sailing? I don't think so. Look at Iraq.”

NATO is still about 450 short of its target for a training force to assist the Afghan security forces, and while that gap apparently was not filled during Friday's session, Clinton said she was not discouraged. “We have a relatively small gap that we're still working to fill. I'm very convinced we'll get that filled,” she said, adding: “For me, the glass is way more than half full.”

Mark Sedwill, the senior NATO civilian representative in Afghanistan, told reporters later that the Tallinn meeting's agreement on starting a transition to Afghan control this year will require endorsement by the Afghan government. That is supposed to happen at a July conference in Kabul.

The next step would be an announcement at a NATO summit meeting in November of the first provinces targeted for transition to Afghan control, Sedwill added.

NATO Secretary General Anders Fogh Rasmussen said the 28-nation alliance is on track with its new strategy for winding down the war in Afghanistan, despite security setbacks and a continuing shortage of foreign trainers for the fledgling Afghan police and army.