WASHINGTON: China might have provided its close ally Pakistan a fairly comprehensive package of proven nuclear weapons design in late 1970s and the CIA knew about it, according to a recently declassified document.

"The CIA had evidence suggesting close Pakistan-China nuclear cooperation , to the point of facilitating a nuclear weapons capability, although the intelligence community saw this as possibly a special case based on an alliance that had existed since 1963," according to recently declassified CIA data, obtained by the National Security Archive (NSA) under the Freedom of Information Act.

According to the document, this allegation has come up before, for example in a state department document and in major news stories but this is the first time the CIA has released some of its own information.

"The estimate highlights some of the main developments, including 'verbal consent (in 1974) to help Pakistan develop a nuclear blast capability', 'hedged and conditional commitment' in 1976 to provide nuclear weapons technology, and unspecified excised information that raised the possibility that China has provided a fairly comprehensive package of proven nuclear weapon design information," it said.

"Even without Chinese help, the Pakistanis could develop a nuclear weapon, but access to Chinese weapons design and test data might be crucial in establishing Islamabad's confidence in an untested weapons capability," said a 1983 national intelligence estimate of the CIA, which is heavily excised.

The exchanges may not have been one-way and the reference to Chinese "involvement" in Pakistan's uranium enrichment programme probably refers to gas centrifuge technology, which Pakistan shared with China, it noted.

Significant portions of the document covering technology sharing are excised, but more may be learned if additional details are released under appeal, the NSA added.