Iran's firebrand President Mahmoud Ahmadinejad announced this week that the Islamic republic's controversial uranium enrichment work had reached an "industrial stage."

But Russia, which is building Iran's first nuclear power plant, and other nations have cast doubts on the substance of his statement.

"Iran is reportedly trying to increase the number of centrifuges. But would this mean complete enrichment?" asked Sergei Kiriyenko, head of the Russian Federal Agency for Atomic Energy.

"We don't think so, according to our experts," he told reporters in Tokyo.

"Simply having numerous centrifuges doesn't mean they can start the enrichment process," he said. "There are many difficult issues that need to be resolved."

Enrichment of uranium is the key sticking point in the standoff between Iran and the West, as the process can produce nuclear fuel but in highly extended form can also make the fissile core for an atomic bomb.

Iran says its nuclear drive is solely aimed at generating energy and that it does not plan to build a military capacity.

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