NATO's decision to scale back joint operations with Afghan forces may protect the lives of Western troops increasingly targeted by "insider attacks," but it raises troubling new questions about President Barack Obama's strategy to stabilize Afghanistan.

After ramping up Afghan security forces at a breakneck rate to allow for a drawdown of Western troops, NATO is coming to grips with a rash of deadly assaults by Afghan recruits who turn their guns on Western allies. Muslim rage over a film insulting the Prophet Mohammad has further stoked the risk.

The White House and NATO leaders have stressed that the suspension of some mentoring operations announced on Tuesday is only a temporary step, limited in scope, that does not alter America's withdrawal timeline. It applies to front-line missions involving units smaller than an 800-strong battalion, and even then, there will be exceptions.

"The president's policy of gradually turning over security lead to Afghan forces continues," White House spokesman Jay Carney told reporters. "It doesn't affect the timeline."

But James Dubik, a retired lieutenant general who oversaw the training of Iraq's security forces, warned that the move would undoubtedly act as a drag on training of Afghan forces, an urgently needed step to prepare them for the time when most NATO combat troops have gone home at the end of 2014.

"As we saw in Iraq and as Afghanistan has seen in the last two years, the partnership program at the company, platoon level is key to the on-the-job training that is required," Dubik said. "So that will be affected and it will be a decelerant in terms of their proficiency."

How much of an impact the restrictions have depends on how long the policy is maintained, he said.

Top brass were under intense pressure to do more to stem a rise in Western casualties at the hands of Afghans they were training - a phenomenon that, by their own admission, they are still struggling to explain.

So far this year, at least 51 NATO troops have been killed in these insider, or "green-on-blue," attacks. That is a spike of more than 45 percent on similar incidents for the whole of 2011.

Taliban blamed

Marine General John Allen, who leads NATO forces in Afghanistan, said last month that about a quarter of the attacks can be blamed on the Taliban, both by direct infiltration of Afghan forces and coercion of Afghan troops to attack their NATO counterparts.

Other attacks are attributed to disputes between Afghan troops and their foreign partners, or chalked up to the violence that comes with the trauma of a decade of war.

Whatever the cause, the Taliban insurgency is almost certain to exploit what it sees as a NATO vulnerability as the last American "surge" troops head home.

The attacks have already prompted several coalition members, including France, to speed up or review plans to withdraw troops ahead of the 2014 deadline to send most NATO combat forces home.

Taliban's last gasp?

U.S. Defense Secretary Leon Panetta, speaking to reporters in Japan on Monday, said the Taliban were resorting to insider attacks as "kind of a last gasp effort" after failing to regain territory they've lost to coalition forces.

Even if that is true, analysts say the obvious political impact that they're having risks emboldening the Taliban, just as Obama brings U.S. troop strength back down to levels before his "surge" of 33,000 forces in 2009-2010.

Jeffrey Dressler, who like Dubik is at the Washington-based Institute for the Study of War, said he believed the move "could cause an increase in attacks ... because it's proven to be effectual."

The policy change came just three weeks after Allen expressed reluctance to scale back partnering with Afghan forces, which he believed increased personal bonds and made U.S. troops safer.

"What we have learned is that the closer the relationship with them - indeed, the more we can foster a relationship of brotherhood, the more secure that we are," he told Pentagon reporters.

House Intelligence Committee Chairman Mike Rogers, however, said Allen and other commanders had little choice but to act, as the number of American and coalition casualties rose.

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"You have to do it," Rogers told Reuters. "They are not able to stop the turning of these individuals and that's the problem. So now you have to take what steps you need to protect our men and women."

(Additional reporting by Tabassum Zakaria; Editing by Warren Strobel, Mary Milliken and Christopher Wilson)