LASHKAR GAH, Afghanistan (AP) -- Afghanistan's president got reassurance Tuesday that NATO intends to backstop his troubled nation's security long beyond 2014, after NATO's chief endorsed keeping Afghanistan's security forces at the current strength for years to come.

NATO Secretary-General Anders Fogh Rasmussen told The Associated Press that keeping the Afghan force larger for longer is more cost effective, and it would be more acceptable to Afghans than foreign soldiers.

He spoke after meeting with Afghan President Hamid Karzai in Kabul on Monday.

"From the political point of view, it is better to give the defense ... an Afghan face, and from an economic point of view, it's less expensive to finance Afghan security forces than to send foreign troops," he said Tuesday as he toured a NATO base in Helmand province.

Fogh Rasmussen was commenting on a proposal favored by the Afghan government -- and debated by NATO ministers in Brussels last month -- to keep 352,000 Afghans in uniform through 2018. NATO is due to turn over security duties to local forces next year and pull out most of its troops. Fogh Rasmussen said most troops in Helmand have already traded combat patrols for advising the Afghans as they do the fighting.

The Afghan army has grown to 184,676 soldiers and the country's police force numbers 146,339 officers, just short of the planned 352,000 total, according to figures shared by NATO this week.

NATO had planned to shrink that combined force to 230,000 next year, but U.S. military and Afghan officials have both suggested keeping the Afghan security forces at their higher "surge" numbers to deal with an expected Taliban onslaught as foreign forces leave.

The "surge" refers to a temporary U.S.-led increase in troops in 2010, aimed at dealing a decisive blow to insurgents, and also to a parallel increase in numbers of Afghan security forces trained and armed by NATO.

The concern for Afghans is that after the NATO drawdown, their green troops could be overrun, and the country plunged back into civil war. Americans worry that the Taliban would use the chaos to regain power, defeating the original purpose of the U.S. military action in 2001.

Cash-strapped NATO members, including the U.S., must figure out who would cover the increased expense for maintaining the Afghan forces at the higher level -- from $4.1 billion annually for the 230,000 troops NATO had planned on, to an estimated $4.8 billion to maintain the surge-level forces.

Fogh Rasmussen says he expects NATO members to make a decision "in a matter of months," likely by summer, as part of their calculations on how many NATO troops to deploy after 2014. U.S. and NATO officials are discussing leaving a residual force of between 8,000 to 12,000 foreign troops to advise and train Afghans after NATO combat operations end.

The White House backs the plan for the Afghan forces, but it must first get through the domestic financial fallout of the automatic spending cuts that kicked in on March 1, dictating mandatory across-the-board reductions in the U.S. federal budget, including defense and foreign aid.

The NATO chief said he and Karzai also discussed signing a long-term security agreement between Afghanistan and NATO, after the U.S. and Afghanistan complete their bilateral security negotiations, possibly by November.

"Once that is concluded, it could serve as a template for a NATO training mission," he said. Fogh Rasmussen added he thought it would be possible to have one agreement covering all nations taking part in the training mission, rather than each nation negotiating with Afghanistan separately. The agreements map out the legal status of foreign forces on Afghan soil.

The NATO chief would not be drawn on Karzai's recent demand that U.S. special operations troops leave Wardak province, following his claims that Afghans linked to U.S. commandos had carried out extrajudicial killings, renditions and torture there. U.S. officials privately denied the charges, while asking Afghan officials to share any evidence they had of such incidents. The officials spoke on condition of anonymity because of the Afghan investigation into the allegations is still ongoing.

Fogh Rasmussen would say only that he expected NATO special operations troops to be a key part of the future mission, especially after his visit with European special forces trainers and their Afghan counterparts at the base in Lashkar Gah.

"No doubt that Afghan special operations forces will be the bedrock of Afghan security in the future, so obviously they will also need our continued training, advice and assistance," he said.

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Kimberly Dozier can be followed on Twitter http://twitter.com/KimberlyDozier