NATO is scaling back joint operations with Afghans after an unprecedented number of Western soldiers were shot dead by their local colleagues and as anger erupts over an anti-Islam film, officers said Tuesday.

The move marks a setback to the US-led strategy for containing an 11-year Taliban insurgency, as a phased withdrawal of Western troops hinges on training and advising Afghan forces to take their place within two years.

But NATO insisted partnering would continue at all levels and rushed to present the move as a change to mitigate the risk of joint operations, rather than a suspension of joint operations.

NATO chief Anders Fogh Rasmussen said the strategy in Afghanistan was unchanged and scaling back joint operations in order to prevent further Western deaths by locals was prudent and temporary.

He said NATO remained committed to seeing Afghans in charge of their own security by the end of 2014.

"That is the bottom line. The goal is unchanged, the strategy remains the same and the timeline remains the same," he said, while rejecting suggestions the move showed insurgents were gaining initiative.

Under the new order, NATO and Pentagon officials said most joint patrols and advisory work with Afghans will be conducted at the battalion level and above.

Cooperation at a lower level will have to be "evaluated on a case-by-case basis and approved by" regional two-star commanders, the International Security Assistance Force (ISAF) said in a statement.

The scale of attacks by Afghan troops against their NATO allies has never before been seen in modern warfare and both sides have struggled to stem the problem.

The US commander in Afghanistan, General John Allen, "has directed all operational commanders to review force protection and tactical activities in the light of the current circumstances", a US military officer in Washington said in an email.

"This guidance was given at the recommendation of, and in conjunction with, key Afghan leaders," said the officer, who spoke on condition of anonymity.

"This will likely lead to adjustments in exactly how, when and where ISAF troops operate, especially during the current period of heightened tension."

Although ISAF called the changes "temporary" they also appeared to be indefinite.

"We can't say how long this measure will linger on and when we can change it back," ISAF spokesman Lieutenant Colonel Hagen Messer told AFP.

Defence Secretary Leon Panetta, speaking at a news conference in Beijing, said the insider attacks were worrying but insisted they would not derail plans to withdraw troops by the end of 2014 as planned.

"We are concerned with regards to these insider attacks and the impact that they're having on our forces. General Allen has reflected that in the steps that he's taken," Panetta said after holding talks with his Chinese counterpart.

The changes also come following violent protests in Afghanistan and around the world over an amateur, American-made film deemed offensive to Islam.

The film coupled with the wave of "green-on-blue" attacks led to the decision to limit the number of joint patrols and operations, Pentagon spokesman George Little said.

Last Friday the Taliban stormed a major NATO base, killing two US Marines and destroying six US fighter jets to avenge the film, kicking off a weekend that saw six ISAF soldiers shot dead by suspected police.

Around 36 insider attacks have claimed the lives of 51 troops in the NATO-led coalition so far this year, sowing mistrust between the Western force and its nominal allies and casting doubt on the credibility of ISAF's "shoulder-to-shoulder" motto.

Commanders believe only a quarter of the assaults are linked to the Taliban and that the remainder were caused by cultural clashes and personal grievances.

The Afghan army and police rapidly expanded into a contingent of nearly 350,000, and critics say the rush to build a large force meant many recruits were not carefully screened beforehand.

NATO did its best to present the operational changes in a positive light, saying it was not a suspension of operations below the brigade level, but a change to how it assesses and mitigates "the risks associated" with such operations.

"In some cases that may mean a temporary separation or tactical pause but it does not mean we have stopped partnered operations," it insisted.

In London, British Defence Secretary Philip Hammond even went so far as to say the decision had not been formalised.

"This is a draft order that ISAF are looking at and it is going to have minimal impact on our operations. There's no change in policy yet," Hammond told reporters.