The commander of NATO forces in Afghanistan said Thursday that the Taliban may be responsible for a greater share of "insider attacks" by Afghan soldiers against foreign troops than previously claimed by the Pentagon.

US General John Allen told reporters that about 25 percent of all so-called "green-on-blue" attacks were the result of the Taliban infiltrating Afghan forces, days after the Pentagon had said an internal review had shown only about 10 percent of all insider assaults could be attributed to the insurgency.

"We think it's about 25 percent," Allen said by video link from Kabul.

When asked about the discrepancy in the numbers, the four-star general said the growing problem still required "lots of analysis."

"The number 10 or 25 is a number we're going to continue to hone to get a feel for this, so we really do have a sense of the size and the magnitude of the enemy threat in the ranks of the Afghan national security forces."

He said the Islamist insurgency was anxious to exploit the incidents for propaganda purposes.

"The Taliban try to take credit for every one of these attacks, whether it's a personal grievance or whether it's a successful infiltration," he said.

NATO has struggled to stem the so-called "green-on-blue" attacks in which uniformed Afghans turn their weapons against their international allies.

A total of 10 soldiers, mostly Americans, have lost their lives at the hands of their Afghan colleagues in the past two weeks, and the attacks have caused almost one in four coalition deaths in the war so far this month.

Allen said the attacks were caused by various factors, including not just Taliban infiltration but "disagreements, animosity which may have grown between the individual shooter and our forces in general, or a particular grievance."

He said that the recent spate of assaults may have been related to the Muslim holy month of Ramadan, as Afghan soldiers were under strain from fasting in intense heat while engaged in combat.

"The daily pressures that are on some of these troops, compounded by the sacrifice associated with fasting, the nature of our operational tempo, remembering that Afghan troops have gone to the field and they have stayed in the field, and they've been in combat now for years, we believe that the combination of many of these particular factors may have come together during the last several weeks to generate the larger numbers that you point to," he said.

Afghan officials on Wednesday said "infiltration by foreign spy agencies" into the ranks of Afghan government forces was to blame for the rise in attacks by Afghan soldiers.

But Allen said the Afghan government had not yet shared information with NATO that proved foreign spies were supposedly behind the incidents.

"I'm looking forward to Afghanistan providing us with the intelligence that permits them to come to that conclusion so that we can understand how they've drawn that conclusion and we could add that into our analysis," Allen said.

The death toll from insider attacks this year has already reached 40, which makes up 13 per cent of all international coalition deaths for 2012.

A Pentagon assessment last year found serious tensions between the NATO-led forces and their Afghan counterparts, fueled by cultural clashes and mistrust.