Pakistan State Oil has cancelled a tender to buy jet fuel for delivery in June amid a border dispute between the South Asian country and Afghanistan, a source at the company said on Tuesday.

PSO initially sought to buy a cargo of 10,000 tonnes of jet fuel for delivery in June but this has now been cancelled due to restrictions in shipping oil across the border, the source said, speaking on condition of anonymity as he was not authorised to speak with media.

About 70 to 80 percent of the company´s imports of jet fuel are re-exported to neighbouring Afghanistan, the source added.

"We still have a cargo waiting to unload outside of Afghanistan and it´s been waiting for the past four to five days," the source said.

US and Afghan special forces, backed by drone strikes and other air support, have waged a series of operations against Daesh in Afghanistan since March, killing dozens of their fighters, mainly in Nangarhar, on the border with Pakistan.

Separately, PSO also cancelled a tender to buy gasoil cargoes for June as it has sufficient inventory, the source said.