WASHINGTON, Oct 12: A prestigious American nuclear watchdog has concluded that the government of Pakistan was not involved with the network of nuclear proliferators who supplied nuclear technology to Iran, Libya and North Korea.

In a recent report - "Uncovering the Nuclear Black Market" - the Washington-based Institute for Science and International Security observes: "The Pakistani government was not directing this network. It was essentially a criminal operation."

But the report also says the fact that a group of individuals were able to run such a network for so long without being noticed by the international community was "more disturbing and dangerous" than if it had been a secret government-controlled effort.

The report, however, warns that investigators have not yet been able to determine the exact involvement of Pakistani government officials in the network and the extent of their awareness of the activities of Dr A. Q. Khan and his associates.

The report says that although the group involved in selling nuclear technology is commonly called the Khan network, it's relatively non-hierarchical.

The key technology holders and several of its leaders were in Pakistan, including Dr Khan. But many other leaders were spread throughout the world and located in Europe, Dubai in the United Arab Emirates, Turkey, South Africa, and Malaysia.

The network also depended on a variety of unwitting manufacturing companies and suppliers on many continents, the report says. The network succeeded in operating in secret for several years before the United States, Britain, and the International Atomic Energy Agency exposed it through a series of actions.

During the IAEA's inspections in Iran during 2003, strong evidence emerged that Pakistani scientists and intermediaries were important clandestine suppliers of centrifuge designs and components to Iran's secret gas centrifuge programme, the report says.

According to the report, US intelligence agencies penetrated at least one part of the Khan network in early last year, which led to the dramatic seizure in October 2003 of several containers of parts bound for Libya's secret centrifuge programme on the ship BBC China.

After Libya renounced nuclear weapons and other weapons of mass destruction in December 2003, US, British, and IAEA investigations learned many details about the activities of the network.

These actions resulted in intensive pressure on Pakistan to conduct a thorough investigation. Once started, the Pakistani investigation led relatively quickly to Dr Khan's confession that he supplied gas centrifuge items to Iran, Libya, and North Korea.

The report claims that the network intended to provide Libya a turnkey gas centrifuge facility. This included 10,000 centrifuges, piping to connect them together, detailed project designs for the centrifuge plant, electrical and electronic equipment, uranium feed and withdrawal equipment.

It also intended to supply the initial 20 tons of uranium hexafluoride, equipment to allow Libya to make more uranium hexafluoride, centrifuge designs, manufacturing equipment and technology to make more centrifuges indigenously.

It also promised to provide on-going technical assistance to help Libya overcome any obstacles in assembling and operating the centrifuges in the plant. The documents Libya has provided to US investigators after agreeing to abandon its nuclear programme appear to contain information Pakistan received from China in the early 1980's, including hand-written notes from lectures given in China, the report says.

The design shown in these documents is that of a Chinese warhead that was tested on a missile, has a mass of about 500 kilograms, and measures less than a meter in diameter.

As part of Libya's abandonment of its nuclear weapons programme, it voluntarily gave the United States, Britain, and the IAEA centrifuge design documents, centrifuge components, and nuclear weapons documents. Libya sent the gas centrifuge items and nuclear weapons documents to the United States for safekeeping.

The report claims those associated with the network sought to capitalize on the elaborate, underground procurement network they had created to supply the Pakistani gas centrifuge programme beginning in the 1970s.

It had many manifestations over the years and involved many people from a variety of countries. Some international suppliers and middlemen had long working relationships with Dr Khan and remained committed to the network for two or more decades, the report claims.

"There was also a familial aspect to the network. Europeans who were involved in the 1970s or 1980s had sons that became involved with them in the 1990s," the report said.

The report says that while investigators now have considerable information about gas centrifuge assistance to Iran and Libya, far less information is available about the gas centrifuge assistance to North Korea.

This deficiency has resulted from North Korea's denial that it has a gas centrifuge programme, the lack of IAEA inspections in North Korea, and Pakistan's reluctance to provide information about its nuclear dealings with North Korea.

The report says that IAEA investigators are now trying to determine whether Iran or North Korea also received nuclear weapon information. The report claims that in late 1990, Dr Khan offered centrifuge help and nuclear weapons design information to Iraq, which requested a sample of the offer but the 1991 Persian Gulf War ended that effort.

Investigators interrogating Dr Khan also probed the possibility of the network's involvement with Syria but Dr Khan denied selling anything to Syria, the report said.