The US and Britain undertook a secret campaign in the late 1970s to prevent Pakistan from going nuclear and unsuccessfully tried to block its attempted covert purchasing of “gray area” technology for its atomic weapons programme, according to declassified documents.

According to the newly declassified State Department Cables, released by the National Security Archive, the U.S. issued 300 demarches to Nuclear Exporters during 1978-1981 in attempt to halt Pakistani nuclear purchases.

At the same time, both Britain and the U.S. kept India in the dark, even as Indian officials had better intelligence information about Pakistan’s nuclear weapons programme.

The documents, however, do not mention the name A.Q. Khan, the National Security Archive said.

But already in late 1978, London and Washington were discovering the footprints of secret Pakistani purchasing organizations that were seeking the technology needed to produce fissile material -- plutonium and highly enriched uranium -- for nuclear weapons, it said.

In November 1978, Britain and the U.S. sent complementary demarches to other members of the Nuclear Suppliers Group (NSG) in efforts to “delay” the Pakistani nuclear programme by denying it access to sensitive technology and equipment.

The U.S. demarche was the first of about 300 sent over the next three years, it said, adding that in its first such demarche, Washington was trying to halt a secret Pakistani effort to continue a plutonium reprocessing facility at Chashma, which the French had begun but had backed out of, partly in response to U.S. encouragement.