Britain's envoy to Afghanistan Sir Sherard Cowper-Coles, has quit amid reports of differences with NATO and US officials over the correct strategy on fighting the Taliban. Sir Sherard was known to have been critical of the US-led military strategy in Afghanistan and to have argued in favour of holding talks with the Taliban. He was appointed in March last year after being UK ambassador in Kabul the two previous years. His resignation came as a premier British thinktank has said that the U.S.-led coalition's strategy in Afghanistan is too ambitious and instead should counter the threat of militant attacks along the Afghan-Pakistan border.International Institute for Strategic Studies (IISS) said in its latest strategic survey report that for Western states to be pinned down militarily and psychologically in Afghanistan will not be in the service of their wider political and security interests.