London, Oct. 7 : US Defense Secretary Robert Gates has accused the British ambassador and top military commander in Afghanistan of being "defeatist" for saying the Taliban could not be beaten.

"While we face significant challenges in Afghanistan, there certainly is no reason to be defeatist or to underestimate the opportunities to be successful in the long run," The Telegraph quoted Gates as saying onboard a military aircraft flying to Europe for NATO meetings.

He was speaking in reaction to comments from Brigadier Mark Carleton-Smith, who said in a newspaper that the war against the Taliban could not be won, and the ambassador, Sherard Cowper-Coles, who said an "acceptable dictator" would be the best political solution for Afghanistan.

Gates, who oversaw the improvement in the war in Iraq, said the coalition would have to negotiate with more moderate Taliban members who were willing to work with the central Afghan government.

"Part of the solution is strengthening the Afghan security forces. Part of the solution is reconciliation with people who are willing to work with the Afghan government," he said.

The approach is demonstrated in a new field manual released by the Pentagon, which for the first time says nation building is as important as winning military battles in fragile states.

The stability operations field manual is derived from the US army''s experience in Iraq and Afghanistan. (ANI)