After being sworn in at the State Department on Wednesday as the top US envoy to Kabul, Lt-Gen Eikenberry will return to the war-torn country where he served as the senior US commander just over two years ago.

Lt-Gen Eikenberry takes the diplomatic stage at a perilous time in the nearly eight-year conflict. Insurgent violence is rising as the Obama administration seeks to implement a new strategy that puts added emphasis on nonmilitary means of stabilizing the country and preventing it from becoming a terrorist haven.

At a retirement ceremony in the Pentagon's Hall of Heroes, Lt-Gen Eikenberry said he will begin his tenure in Kabul under 'extraordinarily difficult conditions' but expressed confidence that the new strategy would succeed.

One of the people he will work with most closely is General David Petraeus, the Central Command chief responsible for US military operations in Afghanistan and Pakistan. Gen Petraeus attended the ceremony, which was hosted by another key figure in the war effort, Admiral Mike Mullen, chairman of the Joint Chiefs of Staff.

The son of a World War II veteran, Lt-Gen Eikenberry has previous experience in the political-military arena, including a stint as the US defence attache in Beijing and as a senior officer at Nato headquarters. He is fluent in Chinese and a scholar of Chinese history. He has two master's degrees - one in East Asian studies from Harvard and another in political science from Stanford.

'Karl Eikenberry's talents are ideally suited to the president's new, comprehensive strategy in which he must get the civilian parts of our effort right,' Adm Mullen said. 'Karl's experience as a soldier and scholar will be crucial to fostering the strong civil-military relationship required to tip the balance.' Lt-Gen Eikenberry joked that he and his wife, Ching, will enjoy a '24-hour vacation' before Wednesday's swearing-in ceremony to be hosted by his new boss, Secretary of State Hillary Rodham Clinton.

Adm Mullen said there have been few instances in US history - perhaps only one or two - in which an American military officer has switched directly out of uniform to become an ambassador. Adm Mullen mentioned no names, but one example is General Maxwell D. Taylor.

According to an official history of the office of the chairman of the Joint Chiefs of Staff, Gen Taylor left as Joint Chiefs chairman to become ambassador to Vietnam in July 1964 at a time of rapidly deepening US military involvement in Vietnam.

Lt-Gen Eikenberry's retirement from active Army duty is effective Friday. He is due to start in Kabul on May 8. -- AP