Tehran's apparent willingness to consider direct talks with nations that have expressed alarm over its nuclear work came as Mahmoud Ahmadinejad, Iran's president, prepared to give a speech marking the country's National Atomic Energy Day.

Nuclear allegations

Western powers have said that Iran is seeking to enrich enough uranium to build a nuclear bomb.

Tehran has denied the allegations, saying its enrichment programme is geared towards producing electricity.

Ahmadinejad is expected to announce on Thursday the testing of new centrifuges at the Natanz uranium enrichment facility and the the inauguration of a fuel-manufacturing plant, both in Isfahan province.

The fuel-manufacturing plant is expected to become operational later this month, the ISNA student news agency reported.

"The ... plant will have the ability to produce the fuel for the 40-megawatt reactor in Arak," the heavy water nuclear plant in Markezi province, ISNA quoted Abdollah Solatsana, deputy head of the Iranian Atomic Energy Organisation, as saying.

Tehran says the reactor will make isotopes purely for agricultural and health purposes, but world powers remain concerned that the plant could be used as part of a nuclear weapons programme.

The International Atomic Energy Agency (IAEA) said in a February 19 report that it had not clarified whether the Arak facility was intended solely for peaceful purposes.

Iran has defied five UN Security Council resolutions calling for a freeze in its enrichment activities, including three resolutions imposing sanctions.

Javier Solana, the European Union head of policy, was on Wednesday asked by world powers to invite Iran to direct talks.

"We reaffirm our unity of purpose and collective determination through direct diplomacy to resolve our shared concerns about Iran's nuclear programme, in line with the package proposals for co-operation with Iran," they said.