Afghanistan's President Hamid Karzai (L) and Britain's Prime Minister David Cameron review an honour guard in Kabul December 7, 2010[Photo/Agencies]

Britain's Prime Minister David Cameron (R) shakes hands with Afghan President Hamid Karzai on arrival in Kabul, Afghanistan December 7, 2010. Cameron, visiting Afghanistan on an unannounced trip, said troops could start withdrawing from the country as early as next year.[Photo/Agencies]