"One can speak of one or two years," Vladimir Dvorkin, a retired general and veteran participant in US-Soviet disarmament talks in the 1970s and 1980s, told reporters when asked how close Iran was to having a nuclear weapon.

"In the technical sense, what may be holding them back is the lack of enough weapons-grade uranium," said Dvorkin, who today heads a strategic arms research centre at the Russian Academy of Sciences in Moscow.

"I consider this a significant threat," said Dvorkin, who stressed that he was voicing his personal views and not those of the Russian government.

"The threat is that Iran, which has effectively ignored all the resolutions and sanctions imposed by the United Nations Security Council, as a nuclear state would become untouchable, allowing it to broaden its support for terrorist organisations such as Hamas and Hezbollah," he said.

Officially, Russian diplomats have downplayed US and Israeli fears that Iran is on the verge of building an atomic weapon, while Moscow has resisted calls for tougher sanctions on Tehran for its disputed nuclear programme.

Russia has also been helping Iran build a civilian nuclear power plant even as Western governments have expressed concern that Tehran's uranium-enrichment programme is aimed at building material for a bomb.

Moscow has also however pointed out that Iran is geographically closer to Russia than to any Western country and has maintained that it is opposed to any effort by Tehran to obtain a nuclear weapons.

Iran denies that it is seeking nuclear weapons at all, saying its nuclear programme is strictly peaceful.

Dvorkin, who helped shape a series of US-Soviet arms control treaties in the 1970s and 1980s, now heads the Centre for International Security at the Institute for World Economy and International Relations in Moscow.

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