NATO said Wednesday that current head Anders Fogh Rasmussen will stay in his post two months longer than previously expected to prepare and oversee the military alliance's next leaders summit in Britain in September.

Rasmussen was initially due to complete his four-year term in July 2013 but that was extended by one year to July 2014.

NATO member ambassadors have now decided that he should stay in office until the end of September 2014 "to enable him to prepare and preside" at the summit in south Wales earlier that month, a statement said.

The last summit was held in 2012 in Chicago.

The 2014 summit comes before the planned withdrawal of NATO forces from Afghanistan, its biggest and longest military operation.

NATO currently plans to maintain a training and assistance mission in Afghanistan post-2014 but its future is in doubt as Afghan President Hamid Karzai is refusing to sign a security pact with Washington on its legal and operational status.

Washington and NATO both say there can be no continued alliance presence in Afghanistan without such a pact.

The Wales summit is also meant to set the guidelines for NATO's future role at a time when defence budgets are under pressure everywhere and as costs for increasingly sophisticated military hardware steadily mount.

The US-led alliance was designed to counter the Soviet threat during the Cold War but after the fall of communism it began a period of active military operations which saw it intervene in the Balkans in the 1990s.

After the 9/11 terror attacks in 2001, NATO took on its biggest commitment, leading the campaign in Afghanistan to oust the Taliban.

Despite initial success and a huge investment in lives and money, the Taliban remain a threat amid doubts that Afghan government forces will be able to hold them at bay after NATO leaves.

Rasmussen, 60 and a former Danish prime minister, was appointed for the maximum single NATO term in 2009.

Among names mentioned as possible successors for a post traditionally held by a European are former Italian foreign minister Franco Frattini, as well as Belgian Defence Minister, Pieter de Crem and Polish Foreign Minister Radoslaw Sikorski who was formerly in charge of defence.