Afghan mission into final phases, says David Cameron
The mission in Afghanistan is moving into its "final phases", David Cameron has said, at a joint press conference with US President Barack Obama.
Speaking at the White House, both leaders stressed that progress had been made in the country - despite losses of US, British and Afghan lives.
International forces will take on a support role from 2013, and Afghans will fully take over security in 2014.
The PM said they would not "give up on this mission", despite its "high cost".
Tensions are high in Afghanistan after an American soldier shot dead 16 Afghan civilians.
On Wednesday evening it emerged that the serviceman had been flown out of Afghanistan to a "pre-trial confinement facility" in another undisclosed country.
Earlier in the day, a member of Nato forces was injured when a stolen truck was driven onto the runway at Camp Bastion, the main British military base in Afghanistan, as US defence secretary Leon Panetta was arriving at the site.
Speaking after talks with Mr Cameron at the White House, the US president said the tragic events of recent days were a reminder of how difficult the mission was.
But he said: "What we can never forget is our forces are making very real progress."
Mr Obama said troops were making headway against the Taliban and al-Qaeda and were training Afghan forces.
He said details of the next stage of transition to Afghan control would be set out at the upcoming Nato summit in Chicago, but added: "This includes shifting to a support role next year in 2013 in advance of Afghans taking full responsibility for security in 2014.
"We are going to complete this mission and we are going to do it responsibly."
BBC political editor Nick Robinson said neither leader wanted to give a more detailed timetable about when troops would leave Afghanistan, but both had stressed they were still ready for the fight in the country, in the face of tough public opinion at home.
Mr Cameron is on a three-day trip to the US and was earlier welcomed to Washington with a 19-gun salute on the South Lawn of the White House.
He said: "We will not give up on this mission because Afghanistan must never again be a safe haven for al-Qaeda to launch attacks against us.
"We will not build a perfect Afghanistan, although let's be clear, we are making some tangible progress.
"But we can help ensure that Afghanistan is capable of delivering its own security without the need for large numbers of foreign troops."
He added: "We are now in the final phases of our military mission.
"That transition to Afghan control, as agreed at Lisbon, is now well under way. And next year, as the president said, in 2013, this includes shifting to a support role."
And he added that he would work with Afghan President Hamid Karzai for a "politically-led solution".
British and US combat troops are expected to leave Afghanistan completely by the end of 2014 - a deadline Mr Cameron said was "achievable and do-able".
'Stop the killing'
The two leaders also discussed Syria, Iran and economic growth.
The United Nations has suggested more than 8,000 people have died since anti-government protests erupted in Syria a year ago, with many casualties in the city of Homs where government forces have been trying to root out rebel fighters.
Mr Cameron said Britain was pledging an additional £2m ($3.1m) for food and medical care, adding: "We must do everything we can to achieve a political transition that will stop the killing."
Earlier, he was greeted by Mr Obama and his wife Michelle, as well as US Secretary of State Hillary Clinton and Vice-President Joe Biden, at the White House.
In remarks ahead of talks, both leaders stressed the strength of the "rock solid" relationship between the UK and US, which Mr Obama said was the "strongest it's ever been".
At a lunch hosted for them, Mrs Clinton also hailed the special relationship, telling Mr Cameron: "No matter what the issue, we stand together."
Later, together with his wife Samantha, Mr Cameron visited the National Children's Centre, which provides care for children with disabilities.
To round off the day, a host of celebrities - including Hollywood star George Clooney and movie mogul Harvey Weinstein - have been invited to the White House for a state dinner
The guest list included UK stars such as Homeland actor Damian Lewis, Northern Irish golfer Rory McIlroy, and Hugh Bonneville and Elizabeth McGovern of ITV period drama Downton Abbey.
Entertainment was to be provided by US R&B star John Legend and British folk group Mumford and Sons, whose singer Marcus Mumford was there with actor girlfriend Carey Mulligan.
UK Chancellor George Osborne and Foreign Secretary William Hague are also in the US for meetings.