VIENNA, Feb 12: The UN nuclear watchdog has uncovered highly-sensitive designs for machines in Iran that can be used to make bomb-grade material , Western diplomats alleged on Thursday. In Berlin, a senior US official repeated Washington's accusation that Iran wants to make a nuclear bomb.

But Iran shrugged off the charges. "The burden of proof is on the one who makes the allegations," Iranian Foreign Minister Kamal Kharazi told reporters in Rome. "There may be questions by IAEA inspectors, but we are ready to verify those."

Several Western diplomats said the International Atomic Energy Agency (IAEA) has found parallels between Libya's nuclear weapons programme and Iran's atomic programme, which Tehran says is purely peaceful.

"They bought the same stuff from the same people," said one Western diplomat who follows the IAEA closely. US Undersecretary of State John Bolton told a security conference in Berlin it was clear what Tehran was up to.

"There's no doubt in our mind that Iran continues to pursue a nuclear weapons programme," said Mr Bolton, described by diplomats in Vienna as one of Washington's hardest hardliners.

Another diplomat said the discovery of designs for gas centrifuges was not because of Iranian cooperation but "good inspection work by the IAEA". He said Iran only admitted it had the designs after the IAEA showed evidence it knew it had them.

Gas centrifuges spin at supersonic speeds to separate fissile uranium 235 from the non-fissile uranium isotopes. The blueprints in question are based on the so-called "G2" centrifuge developed by the British-German-Dutch enrichment consortium Urenco. There were no indications Urenco, which denied selling technology to Iran, provided the designs.

The steel G2 centrifuge is better than the earlier aluminium G1, a version of which Iran has already been mass producing. After keeping its enrichment programme a secret for 18 years, Iran gave the IAEA in October what it said was a full declaration of its nuclear programme. But it did not mention the G2-based centrifuge designs, diplomats said.

Diplomats said Libya has told the IAEA exactly what it bought, when and from whom. They said many purchases were handled through an illicit network based in Dubai and linked to Dr Abdul Qadeer Khan.

The IAEA has been investigating the global nuclear black market that helped Iran, Libya and North Korea bypass international sanctions and purchase sensitive nuclear technology that could be used to make weapons.

Gary Samore, head of the International Institute for Strategic Studies and an adviser to former US President Bill Clinton, said the discovery of the designs raises the question of whether Iran has a hidden enrichment facility.

"There's always been a suspicion that Iran got the more advanced (G2) and there's some concern that they might be building an undeclared facility someplace that would utilise both the G1 and G2 for the production of weapons grade uranium," Mr Samore said.

Diplomats said it was unclear if Iran had been manufacturing or procuring G2-compatible components or actual centrifuges. This issue will likely be discussed in an IAEA report on Iran expected to be circulated among Vienna diplomats next week.

"This (design discovery) raises very serious questions that we will address at the upcoming IAEA board meeting (on March 8)," a Western diplomat said. Diplomats said the designs could give Washington new ammunition in its drive to report Iran to the UN Security Council for concealing the extent of its nuclear programme. The Council can impose economic and diplomatic sanctions. -Reuters/AFP