US Vice-President Joe Biden has told the BBC that the war in Afghanistan is in the interests of the US and the UK, reported BBC.
"It is worth the effort we are making," he said in an interview with the BBC's Jonathan Beale.
He also insisted the US would be able to close Guantanamo Bay prison by January, as planned, but that each case had to be considered individually.
Mr Biden was speaking during a European trip in which he has visited Ukraine and Georgia.
'Courageous warriors'
The vice-president insisted that "in terms of national interest of Great Britain, the US and Europe, [the war in Afghanistan] is worth the effort we are making and the sacrifice that is being felt".
And he reiterated the Obama administration's rationale for the conflict.
"This is the place from which the attacks of 9/11 and all those attacks in Europe from al-Qaeda have flowed - from Afghanistan and Pakistan."
Mr Biden was full of praise for British troops, calling them "among the best trained and bravest warriors in the world".
But he was unable to comment on the standard of equipment that British troops had been given.
A political row has broken out in the UK over the adequacy of British troops' equipment, after Foreign Office Minister Lord Malloch Brown told a reporter that "we definitely don't have enough helicopters".
Lord Malloch Brown later withdrew his remarks.
Critics say British troops' lack of helicopters has made them more vulnerable to roadside explosives.
Mr Biden said that he was "not in a position to make a judgement" but said he assumed they had all they needed.
Asked about the recent announcement that a report on the closure of the Guantanamo Bay prison camp was being delayed, Mr Biden said the administration had been busy trying to determine what should happen to each of the detainees held there.
"We are going through every single detainee's records ... to make a judgement about whether or not they should be tried [or] ... released and if so what country might take them if we can't get them back to the country of origin because they're going to be tortured or mistreated," he said.
But he expressed confidence that the camp would still be closed according to the timetable laid out by President Barack Obama in January, and hinted that some of the detainees would be retained at another prison.
"We expect before January - well before January - we will have a decision on each and every individual being held."