WASHINGTON // The founder of Pakistan's nuclear bomb programme said the government of North Korea bribed top military officials in Islamabad to obtain access to sensitive nuclear technology in the late 1990s.

Abdul Qadeer Khan has made available documents that he said support his claim that he transferred more than US$3 million (Dh11m) in payments by North Korea to senior officers in the Pakistani military, which he said subsequently approved his sharing of technical know-how and equipment with North Korean scientists.

Mr Khan also has released what he said is a copy of a North Korean official's letter to him in 1998, written in English, that spells out details of the clandestine deal.

Some Western intelligence officials and other experts have said that they think the letter is authentic and that it offers confirmation of a transaction they have long suspected but could never prove. Pakistani officials, including those named as recipients of the cash, have called the letter a fake. Mr Khan, whom some in his country have hailed as a national hero, is at odds with many Pakistani officials, who have said he acted alone in selling nuclear secrets.

If the letter is genuine, it would reveal a remarkable instance of corruption related to nuclear weapons. US officials have worried for decades about the potential involvement of elements of Pakistan's military in illicit nuclear proliferation, partly because terrorist groups in the region and governments of other countries are eager to acquire an atomic bomb or the capacity to build one.

Because the transactions in this episode would be directly known only to the participants, the assertions by Mr Khan and the details in the letter could not be independently verified. A previously undisclosed US investigation of the corruption at the heart of the allegations - conducted before the letter became available - ended inconclusively six years ago, in part because the Pakistani government has barred official Western contact with Mr Khan, US officials said.

By all accounts, Pakistan's confirmed shipments of centrifuges and sophisticated drawings helped North Korea develop the capacity to undertake a uranium-based route to making the bomb, in addition to its existing plutonium weapons. Late last year, North Korea let a group of US experts see a uranium-enrichment facility and said it was operational.

The letter Mr Khan released, which US officials said they had not seen previously, is dated July 15, 1998, and marked "Secret". The "3 millions dollars have already been paid" to one Pakistani military official and "half a million dollars" and some jewellery had been given to a second official, the letter says, which carries the apparent signature of North Korean Workers Party secretary Jon Byong Ho. The text also says: "Please give the agreed documents, components, etc to a … [North Korean Embassy official in Pakistan] to be flown back when our plane returns after delivery of missile components."

The North Korean government did not respond to requests for comment about the letter.

Jehangir Karamat, a retired Pakistani military chief named as the recipient of the $3 million payment, said the letter is untrue. In an e-mail from Lahore, Gen Karamat said Mr Khan, as part of his defence against allegations of personal responsibility for illicit nuclear proliferation, had tried "to shift blame on others". He said the letter's allegations were "malicious with no truth in them whatsoever."

The other official, retired Lt Gen Zulfiqar Khan, called the letter "a fabrication".

A senior Pakistani official, who asked not to be named "to avoid offending" Mr Khan's supporters, said the letter "is clearly a fabrication. It is not on any official letterhead and bears no seal. The reference to alleged payment and gifts to senior Pakistani military officers is ludicrous."

There is, however, a Pakistani-Western divide on the letter, which was provided by the former British journalist Simon Henderson. A US intelligence official who tracks nuclear proliferation matters said it contains accurate details of sensitive matters known only to a handful of people in Pakistan, North Korea and the United States.

A US official said separately that government experts concluded after examining a copy of the letter that the signature appears authentic and that the substance is "consistent with our knowledge" of the same events.

Olli Heinonen, who has worked for 27 years for the International Atomic Energy Agency ad who led its investigation of Mr Khan before moving to Harvard Kennedy School in the US last year, said the letter is similar to other North Korean notes that he had seen or received. They typically lacked a letterhead, he said. Moreover, he said he has previously heard similar accounts - originating from senior Pakistanis - of clandestine payments by North Korea to Pakistani military officials and government advisers.

The substance of the letter, Mr Heinonen said, "makes a lot of sense," given what is now known about the North Korean programme.

Mr Jon, now 84, the North Korean official whose signature appears on the letter, has long been a powerful member of North Korea's national defence commission, in charge of military procurement. In August, the US Treasury Department imposed financial sanctions on his department for its ballistic missile work.

* The Washington Post