Iranian President Mahmoud Ahmadinejad is to unveil several unspecified nuclear "achievements" on Wednesday, his government's website said.

"Several completed nuclear projects will be unveiled tomorrow in the presence of the president," the official website said on Tuesday.

"Experts believe these achievements will show the world the extraordinary capability and knowledge of Iranians."

It added that the progress will underline Iran's scientific adherence to "nuclear power for all and nuclear weapons for none," the website said.

The announcement confirmed a vow made by Ahmadinejad on Saturday to inaugurate "important nuclear projects" within "days," in a speech marking the anniversary of Iran's 1979 Islamic revolution.

Iran's progress in its nuclear programme has deeply unsettled the West and Israel, which see it masking a drive for atomic weapons. A report by the UN nuclear watchdog in November also expressed strong suspicions in that sense.

Tehran, though, has repeatedly said its nuclear activities are exclusively peaceful in nature.

The international showdown over Iran's nuclear programme has deepened in recent months, with the United States and the European Union slapping unprecedentedly tough economic sanctions on the Islamic republic to pressure it to halt its activities.

Israel has threatened to possibly unleash air strikes against Iranian nuclear facilities, while the United States has intimated it, too, could take military action if it thought it necessary.

Iran has reacted defiantly, beginning uranium enrichment in a fortified bunker under a mountain in Fordo, near the holy city of Qom, and promising soon to insert its first domestically made nuclear fuel plates into its Tehran research reactor.

It has also claimed to be ready to resume stalled talks with world powers over its nuclear programme but has yet to formally reply to a letter sent by EU foreign policy chief Catherine Ashton nearly four months ago offering negotiations.