UN inspectors sifting through Iran's nuclear files have discovered drawings of high-tech equipment that can be used to make weapons-grade uranium -- a new link to the black market headed by the father of Pakistan's atomic bomb, diplomats said Thursday.

Beyond adding another piece to the puzzle of who provided what in the clandestine supply chain headed by Abdul Qadeer Khan, the revelations cast fresh doubt on Iran's commitment to dispelling suspicions it is trying to make atomic arms. But Iran insisted Thursday that it was cooperating.

The diplomats, who spoke on condition of anonymity, said the designs were of a P-2 centrifuge -- more advanced than the P-1 model Iran has acknowledged using to enrich uranium for what is says are peaceful purposes. They said preliminary investigations by inspectors working for the International Atomic Energy Agency indicated they matched drawings of equipment found in Libya and supplied by Khan's network.

While highly enriched uranium is a key component of some nuclear warheads, less enriched uranium can be used to generate power, which is what Iran says it was interested in.

The diplomats said Iran did not volunteer the designs -- despite pledging last year to replace nearly two decades of secrecy with full openness about all aspects of its nuclear activities. Instead, they said, IAEA inspectors had to dig for them.

"Coming up with them is an example of real good inspector work," one of the diplomats told The Associated Press. "They took information and put it together and put something in front of them that they can't deny."

The diplomats said Iran had not yet formally explained why the advanced centrifuge designs were not voluntarily handed over to the agency.

Still, the diplomats emphasized that -- despite putting into question Iran's pledge to be fully open -- the find did not advance suspicions that Tehran was trying to make nuclear weapons.

The United States and others accuse Iran of having nuclear weapons ambitions. Iran agreed to end nearly two decades of nuclear secrecy late last year but only under intense international pressure generated by the discovery of its enrichment program.

"We're not convinced Iran has come completely clean," US Undersecretary of State John R. Bolton told a security conference in Berlin. "There is no doubt in our minds that Iran continues to pursue nuclear weapons. They have not complied even with the commitment they made in October."

Bolton was speaking generally, not in response to the discovery of the drawings.

In Rome, Iranian Foreign Minister Kamal Kharrazi denied Tehran had any nuclear weapons ambitions.

"We do not have anything to hide and we are ready to be inspected more (seriously) by IAEA inspectors," Kharrazi told reporters on the sidelines of a conference celebrating 50 years of Vatican-Iranian relations.

"There may be questions by IAEA inspectors but we are ready to verify those, and what has been achieved altogether up until now is out of our cooperation with IAEA," Kharrazi said in English when asked about the discovery of the drawings. "As long as we are ready to continue our cooperation, all outstanding questions will be verified."  

On Wednesday, US President Bush acknowledged loopholes in the international enforcement system and urged the United Nations and member states to draft criminal penalties for nuclear trafficking.

While accusing Khan of being the mastermind of a clandestine nuclear supply operation, Bush avoided criticism of the Pakistani government, a key ally in the fight against terror. Pakistani President Pervez Musharraf says his government knew nothing of Khan's network, even though his military controlled the nation's nuclear program.

Khan, a national hero in Pakistan for creating a nuclear deterrent against archrival India, confessed on Pakistani television last week to masterminding a network that supplied Libya, Iran and North Korea with nuclear technology. Musharraf then pardoned him.

In a speech Thursday, Musharraf said help with nuclear proliferation had come from different countries -- not just Pakistan.

"But things happened from here also, and we need to correct our house," he said. "We are a responsible nation. We must not proliferate."

Earlier this year, Libya handed over engineers' drawings of a crude nuclear warhead linked to Khan as part of its decision to scrap all programs aimed at making weapons of mass destruction.

Malaysia pledged Thursday to share information with Washington from its investigation of B.S.A. Tahir, a man Bush described as a major player in the trafficking network. But top Malaysian officials insisted the sole known case of Malaysian involvement was the unwitting manufacture of parts seized en route to Libya last year.

Also Thursday, China declared it had a "common interest" with Washington in halting illicit arms trafficking. Foreign Ministry spokeswoman Zhang Qiyue said Beijing would take "effective measures" to enforce rules against exports of weapons technology by Chinese companies.

In Moscow, Russian nuclear energy minister Alexander Rumyantsev postponed a trip to Iran next week because the countries have not nailed down agreements involving a reactor Russia is building. Russia has been under pressure to freeze the US$800 million deal, with Washington saying the facility could help Iran develop weapons.

(China Daily February 13, 2004)