BRUSSELS - NATO's top commander in Afghanistan offered a cautiously optimistic assessment of the transition of security duties to Afghan forces during a briefing with alliance representatives Wednesday, a U.S. official said.

Gen. David Petraeus and his civilian counterpart, Ambassador Mark Sedwill, addressed the alliance a day before the first-ever joint conference of foreign and defence ministers from NATO's 28 states, including top U.S. officials.

The briefing focused on plans to start handing over security duties to the Afghan forces, which are due to start next year.

"There are areas of the country that are reasonably secure already, and Afghan security forces are capable of handling security already," Sedwill told reporters after the session.

He noted, however, that the precise timing will depend upon conditions on the ground, and that the transfer will not start everywhere in 2011. "In some areas that are contested it will not start for a year or 18 months later," he said.

The process should be completed by 2014, although some allied troops -- including special forces and trainers -- will remain in Afghanistan after that date, Sedwill said.

NATO's first ground war in its 42-year history is entering its 10th year. Nearly 150,000 international troops, along with some 220,000 government security forces, are still struggling to gain the upper hand in the war that recently entered its 10th year. They face an estimated 30,000 insurgents.

U.S. and NATO forces are expected to begin leaving Afghanistan next year. But Washington and its allies are expected to continue providing massive financial aid to Kabul for years to come.

"We know the Afghan security forces will need $6-8 billion a year, which will have to be underwritten by the international community," Sedwill said.

Also Wednesday, U.S. Defence Secretary Robert Gates warned that the alliance should not be too quick to hand over control of even districts that might seem safe now.

"What's needed is a more strategic approach, because the worst thing that could happen is to turn one of these over," only to see the Taliban regroup, he told reporters travelling with him to Brussels.

Thursday's meeting of defence and foreign ministers in Brussels will consider changes in the alliance's mission statement, attempting to bridge a rift between the U.S., which favours a greater international role for the alliance, and European nations that want it to retain its traditional defensive focus.

NATO Secretary-General Anders Fogh Rasmussen said the ministers will focus on reforming the Cold War alliance to allow it to deal with emerging threats such as ballistic missiles and cyber warfare.

Their recommendations will pave the way for a summit of the alliance's heads of state and government in Lisbon, Portugal, on Nov. 19-20, when Rasmussen will officially unveil NATO's new strategic concept.

The previous mission statement focused mainly on NATO's peacekeeping role in places such as Bosnia and Kosovo. It was adopted in 1999, soon after the end of the Cold War and before the Sept. 11, 2001, attacks in the United States forced the alliance to take on missions such as counterinsurgency warfare in Afghanistan.

Washington now wants NATO to be prepared to contribute forces to missions outside its traditional theatre of operations in Europe, such as in Afghanistan or the anti-piracy naval patrols in the Indian Ocean. But many European governments remain wary, arguing that the alliance should not be transformed into a global policeman.

"Everyone has a different vision of security threats," said Jim Townsend, U.S. deputy assistant secretary of defence. "Some look east, some look west, some are concerned about territorial defence, some about weapons of mass destruction."

"There are a lot of missions where NATO needs to go, and when you try to write a document that strikes a balance that's pretty difficult," he told reporters Tuesday.

Critics already have noted that the new mission will have to paper over sharp rifts between NATO nations.

"What is quickly becoming clear is that there are a number of disagreements and ultimately incompatible views among NATO member states," said Marko Papic, an analyst for the U.S. security think-tank STRATFOR.

"This will ultimately mean that the new strategic concept presented to heads of government on Oct. 20 will be particularly bland and full of inconsistencies," he said in a telephone interview from Austin, Texas.