A secret US military report says that the Taliban, backed by Pakistan, are set to retake control over Afghanistan after Nato-led forces withdraw from the country, Britain's Times of London newspaper reported.

Lt Col Jimmie Cummings, a spokesman for the Nato-led International Security Assistance Force (ISAF), confirmed the document's existence but said it was not a strategic assessment of operations.

"The classified document in question is a compilation of Taliban detainee opinions. It's not an analysis, nor is it meant to be considered an analysis," he said.

Nevertheless, it could be interpreted as a damning assessment of the war, now dragging into its 11th year and aimed at blocking a Taliban return to power, or possibly an admission of defeat.

It could also reinforce the view of Taliban hardliners that the group should not negotiate peace with the US and President Hamid Karzai's unpopular government while in a position of strength.

The document cited by the Times said that Pakistan's powerful security agency, the Inter-Services Intelligence (ISI), was assisting the Taliban in directing attacks against foreign forces, a charge often denied by Islamabad.

The allegations drew a strong response from Pakistani Foreign Ministry spokesman Abdul Basit. "This is frivolous, to put it mildly," he said. "We are committed to non-interference in Afghanistan."     

The Times said the "highly classified" report was put together by the US military at Bagram air base in Afghanistan for top Nato officers last month. The BBC also carried a report on the leaked document.        

Large swathes of Afghanistan have already been handed back to Afghan security forces, with the last foreign combat troops due to leave by the end of 2014. But many Afghans doubt their army, security forces or police will be able to take firm control of one of the world's most unstable countries once foreign combat troops leave.

The US embassy in Kabul declined to comment on the report. The accusations will likely further strain ties between Western powers and Islamabad, which has long denied backing militant groups seeking to topple the US-backed government in Kabul.

Pakistani Foreign Minister Hina Rabbani Khar was visiting Kabul on Wednesday on a mission to repair strained diplomatic ties with Afghanistan's government and to meet Karzai to discuss possible peace talks with the Taliban.

Pakistan is currently reviewing ties with the US which have suffered a series of setbacks since a unilateral US raid that killed Osama bin Laden on Pakistani soil in May last year humiliated Pakistan's powerful generals. A November 26 cross-border Nato air attack that killed 24 Pakistani soldiers deepened the crisis. - Reuters