Officials have said that Britain's special envoy to Afghanistan, often at odds with NATO and the United States over the conduct of the war with the Taliban, has resigned.

The Guardian reported on Monday that a spokesman for the British government said Sir Sherard Cowper-Coles has taken an "extended leave."

The newspaper further said that Cowper-Coles has clashed with senior NATO and U. S. officials by insisting the military campaign against the Taliban was destined to fail and that direct talks with the insurgents should be a priority.

Afghan President Hamid Karzai and U. N. Secretary-General Ban Ki-moon, in July, will host an international conference in Kabul that is expected to focus on the controversial issue of talks with the Taliban.

Cowper-Coles, a career diplomat who has served in Saudi Arabia and in Israel, was U. K. ambassador to Kabul from 2007 to 2009, and was appointed special representative in February 2009.

The Guardian has reported that Cowper-Coles is said to have pushed strongly for the withdrawal of British troops from Afghanistan as early as possible. (With Inputs from Agencies)