A leading US think-tank has accused members of Pakistan's intelligence service, the ISI, of aiding Taleban fighters in neighbouring Afghanistan.
In a new report, funded by the Pentagon, the Rand Corporation said individual Pakistani agents had provided intelligence to insurgents.
Pakistan has always denied such allegations in the past.
The Rand report says Pakistani sources tipped off the Taleban about the movement of Afghan and foreign forces.
This had undermined several American and Nato operations, the report said.
The Rand report also said that some of the ISI staff gave the Taleban financial help and organised medical care for wounded militants.
Last month, Nato criticised negotiations between Pakistan's new government and the Taleban, saying cross-border attacks in Afghanistan were on the rise.
Pakistan's army has swapped prisoners with the Taleban and cut troop numbers in a tribal area near Afghanistan, stirring growing alarm in the West.
Nato and the US say such deals have led to "safe havens" for the Taleban and al-Qaeda along the border. Source:BBC News