US President Barack Obama, during his unannounced visit to Afghanistan, assured his counterpart Hamid Karzai of smooth transition of the country's security to Afghan forces as American troops will begin winding down next summer.

"Both Presidents reviewed for one another and then reaffirmed their commitment to the two major deliverables coming out of Lisbon — the first is this framework for security transition that is due to begin in early 2011, and then conclude by the end of 2014," Douglas Lute, senior advisor and coordinator for Afghanistan and Pakistan said.

Mr Obama and Mr Karzai have prioritised the security transfer in Afghanistan and said both nations should build on the momentum set at Lisbon, where the US President stressed that he wants his troops out of major combat in Afghanistan by the end of 2014, the date he and other Nato leaders set for moving Afghans into the lead role in fighting the Taliban.

"We intend that all 34 provinces in Afghanistan will have passed onto the lead security responsibility to the Afghan security forces. So they (Obama and Karzai) reaffirmed their commitment to that," Lute told reporters onboard Air Force One on his way back to Washington from Kabul, where the US President made a surprise visit for a few hours on Friday.

The visit comes nearly two weeks after both the leaders met in Lisbon, Portugal, on the sidelines of the Nato Summit. Because of bad weather, Mr Obama could not move out of the Bagram Air base to meet Karzai at the Presidential Palace. The two leaders spoke to each other on the phone, lasting for 15 minutes.

"The two Presidents agreed that work on a similar bilateral partnership declaration needs to continue and conclude in the early months of 2011, and we're on track to do that. They both reaffirmed their commitment to finishing up this bilateral arrangement as well," Lute said.

Mr Obama and Mr Karzai also discussed "an enduring commitment even beyond 2014," once Afghans assumes the security lead. "You’ll recall that in Lisbon the Nato secretary general and President Karzai signed a declaration, a statement of intent to continue this longstanding, enduring commitment of Nato supporting Afghan security forces," the advisor said.

President Karzai thanked Mr Obama and his troops for fighting a nine-year-long battle in Afghanistan against terror. Mr Obama wished Mr Karzai for a good holiday season as he hoped the weather would improve for the scheduled visit of Pakistani Prime Minister Yousuf Raza Gilani to see the Afghan President, Lute said.

On leaked diplomatic cables, Lute said the latest WikiLeaks expose did not come for discussions. "They have talked about this before in their periodic discussions, but it did not come up today."

US secretary of state Hillary Clinton has already spoken to Mr Karzai about it and Karl W Eikenberry, US ambassador to Afghanistan, then went to brief the Afghan government about what was expected in these WikiLeaks, Lute said.

"So there had already been consultation with the Afghan government about this in the previous several days, just as the State Department has been running consultations with governments around the world what we thought to be in the cables," he added.