BRUSSELS - NATO is strongly considering a proposal to continue funding a security force of 352,000 Afghan troops through 2018, as part of an effort to maintain security and help convince Afghanistan that America and its allies will not abandon it once combat troops leave in 2014, senior alliance officials said Thursday.

Such a change, if NATO endorses it, could increase the costs to the U.S. and allies by more than $2 billion a year, at a time when most are struggling with budget cuts and fiscal woes. Last May, NATO agreed to underwrite an Afghan force of about 230,000, at a cost of about $4.1 billion a year after 2014. It costs about $6.5 billion this year to fund the current Afghan force of 352,000, and the U.S. is providing about $5.7 billion of that.

Maintaining the larger troop strength could bolster the confidence of the Afghan forces and make it clear that NATO is committed to an enduring relationship with Afghanistan, a senior NATO official said.

The officials spoke on condition of anonymity because they were not authorized to discuss the plan publicly.

Asked about the plan, NATO Secretary-General Fogh Rasmussen confirmed to reporters that it was under consideration.

"I feel confident that we will be able to finance Afghan security forces of that size," he said.

He added that Afghans can't afford a security force of 352,000, so the funding would be the responsibility of the whole international community.

"From the economic point of view, it is actually less expensive to finance Afghan Security Forces than to deploy foreign troops," he said.

That argument, however, may be a harder sell in the U.S. Congress, where lawmakers are deadlocked over how to solve the budget crisis that is set to trigger furloughs for 800,000 federal workers in the Pentagon alone, along with $85 billion in broad, automatic spending cuts across the government.

NATO defense ministers, including outgoing U.S. Defense Secretary Leon Panetta, are meeting here and discussing progress in the Afghan war and the ongoing drawdown of troops. President Barack Obama announced in his State of the Union address that he will withdraw 34,000 American troops from Afghanistan by this time next year. There are about 66,000 there now.

Other NATO nations are also evaluating their commitments to the war, and officials are meeting to encourage allies to participate in the effort to continue to train and advise the Afghan forces after 2014.

According to one of the NATO officials, uncertainty about the future is a critical worry in Afghanistan.

Afghans are still troubled by memories of 1989, when the Soviets withdrew from Afghanistan in defeat, and Washington then withdrew support for anti-Soviet militia forces there, setting the stage for Taliban rule. The Taliban then allowed al-Qaida to use the country to plan the terror attacks of Sept. 11, 2001.

Many Afghans still believe the U.S. will abandon the country again when the combat is over, while others believe Taliban assertions that the coalition troops will stay as an occupying force. In the coming months, the official said it will be important to show the Afghans that NATO allies will continue to support the country after 2014, while also proving that the local forces will be in charge of security for their own nation.

Such intangible issues, the official said, present a greater problem at this point than some of the other more obvious challenges, such as improving the quality of the Afghan forces, battling the Taliban and getting the U.S. troops and equipment out by the end of 2014.

The official said Afghan troops worry that if the size of the force is cut, they will be out of a job after 2014. As a result, they may not concentrate on building better military units and instead focus on how they will care for their families or get money when the tap runs dry.

Making the Afghans more confident about the future will encourage them to spend the next 23 months working with allies, the official said.

On the sidelines of the meeting Thursday, Panetta met with Afghan Defense Minister Bismullah Khan Mohammadi to discuss the ongoing transition of security to the Afghan forces.

That transition is well underway, as the Afghan security forces are taking the lead for security in about 90 percent of the country. That shift has become apparent in the casualty figures, with eight coalition troops _including three Americans — killed so far this year. Overall last year, 295 U.S. troops were killed compared to 1,200 Afghan soldiers, according to data compiled by the Washington-based Brookings Institution.

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Associated Press Writer Don Melvin contributed to this report.

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Lolita C. Baldor can be followed on Twitter at http://twitter.com/lbaldor