Nato endorses Afghanistan withdrawal timetable
Nato leaders meeting in Chicago have endorsed plans to hand over combat command to Afghan forces by mid-2013.
They confirmed Nato's combat troops would be withdrawn by the end of 2014, with only training units remaining.
But US President Barack Obama pledged that: "As Afghans stand up, they will not stand alone."
Nato also said it was optimistic Pakistan would reopen supply routes that were closed after a US air strike in 2011 killed 24 Pakistani soldiers.
The two-day meeting brought together leaders from more than 50 nations, including 28 Nato countries, as well as Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari.
Nato's summit statement stressed that the transition to Afghan control was "irreversible" and that no combat mission would remain after the end of 2014, when 130,000 Nato-led troops are scheduled to have left.
However, Mr Obama issued a pledge to stand by the Afghan people.
He said Nato would continue to "advise and assist Afghan forces as they grow stronger".
But he added: "The Afghan forces will never be prepared if they don't start taking responsibility."
Mr Obama said there would "never be an optimum point where we can say this is all done - it's a process and sometimes a messy process".
But he said: "The coalition is committed to the plan to bringing the war in Afghanistan to a responsible end."
Although the timetable had risks, Mr Obama said he believed it was "sound and responsible".
Nato Secretary General Anders Fogh Rasmussen touched on the question of the funding of Afghan security forces post-2014, denying that the summit was intended to be a pledging conference.
He said he was pleased a number of countries had made new pledges and denied there was any shortfall in funds.
Mr Rasmussen said: "We are on the right track to reaching the goal of around $4bn a year for financing of Afghan security forces - it's a positive story."
However, the question of the Pakistani supply route has cast a shadow over the summit.
Mr Rasmussen denied that Mr Zardari had been invited to the summit to seal a deal on reopening the supply routes, saying: "We did not expect an agreement on Pakistan transit routes to be reached at this summit."
Mr Obama agreed, saying: "We didn't anticipate the supply issue would be resolved but we are making diligent progress."
Mr Rasmussen said the closure had so far not had a major impact on Nato operations but would constitute a logistical challenge when the draw-down of troops began.
He added: "We would like to see the reopening of the routes as soon as possible... the ones through Pakistan are of great importance and I would expect a reopening of the transit routes in the very near future."
Mr Zardari was quoted as saying that his government was in favour of reaching a deal with Nato on the supply routes.
Mr Obama, who said he had only had a brief discussion with Mr Zardari, admitted there had been tension with Pakistan "over the past several months".
He said he did not want to paper over those cracks, but insisted the problems were being worked through.
The supply route was closed in November after the US air strike.
Frictions with Pakistan appeared to continue at the summit - Mr Zardari sat in a meeting as Mr Obama thanked Afghanistan's other neighbours for allowing war supply shipments to be expanded since the closure of the Pakistani routes.
The US president also gave a warning to Islamabad. "Ultimately it is in our interest to see a successful, stable Pakistan and it is in Pakistan's interests to work with us and the world community to ensure that they themselves are not consumed by extremism that is in their midst," he told reporters at the closing news conference.
Mr Rasmussen said the Chicago summit had been "highly successful" in "renewing the unbreakable bond between North America and Europe".
He said: "Nato is fit to face the future, no matter what the future brings."
Mr Cameron said that Nato had agreed it needed a "new mindset".
He said: "Nato should look outwards, reassert its relevance and be ready to tackle threats that may lay outside its territories" but which continue to be a risk to its members.
Mr Cameron also addressed the Taliban, saying: "The message to the insurgency is equally clear: You can't win on the battlefield; stop fighting and start talking."
More than 10 years after the US toppled the Taliban regime, violence is continuing unabated in Afghanistan.
According to UN figures, the number of deaths reached a record 3,031 in 2011 - the great majority caused by militants.