In a move that will heighten tensions with the West, Tehran informed the International Atomic Energy Agency (IAEA) that on January 9 it would restart nuclear research and development work, which had been suspended under an agreement with the European Union just over a year ago. "The IAEA has been informed that Iraq will restart research on the technology of nuclear fuel in a few days, with the co-operation and co-ordination of the agency," Mohammad Saidi, the deputy head of Iran ’s atomic energy agency, said. "We think our experts have undergone many losses during this period [of suspension]. Many of our researchers have lost their jobs."

Iran did not specify what the work would comprise. There were fears yesterday that it could be related to the enrichment of uranium, which is used as a nuclear fuel and, in its highly enriched form, the core of an atomic bomb.

Western intelligence agencies have reported that Iran is actively shopping around for nuclear weapons components.

The IAEA said that it was seeking clarification from Iran. Mohammad ElBaradei, the agency’s director-general, urged Iran to respect the freeze on all "enrichment-related activity".

Britain, which with France and Germany is due to resume talks with Iran over its nuclear programme this month, described Tehran’s decision as "unhelpful and provocative".

One possible solution envisages allowing Russia to conduct the enrichment work on Iran’s behalf, but that was dismissed by Iran yesterday.

"The Russian proposal is ambiguous," Hamid Reza Asefi, the Iranian Foreign Ministry spokesman, said. "If they want to propose enrichment [only] in Russia we have said it is not acceptable."

The hardening of Iran’s position is seen as further evidence that President Ahmadinejad is intent on pressing ahead with Iran’s nuclear programme regardless of Western concerns. Soon after his election last year, Iran resumed uranium conversion at its facility near Isfahan.

If evidence emerges that it is conducting enrichment as well, it could be referred to the United Nations Security Council for possible sanctions when the IAEA board meets in March.

President Ahmadinejad shows no signs of abandoning his aim of returning Iran to the revolutionary ideals espoused by Ayatollah Khomeini when he came to power in 1979. Yesterday he said that the country’s 16-year policy of détente with Europe pursued by his two predecessors had failed.

In a closed meeting with parliament’s national security and foreign policy commission, he said that the period under Ali Akbar Hashemi Rafsanjani had seen the "collapse of our foreign policy" while under Mohammad Khatami, Iran was "alienated from our revolutionary goals".

The US responded to the latest Iranian statement by threatening to seek international action if Tehran resumed nuclear fuel research. Sean McCormack, a State Department spokesman, accused the Iranians of doing a "bob and weave" in negotiations. "Our view is that if Iran takes further enrichment-related steps, the international community will have to consider additional measures to constrain Iran’s nuclear ambitions," he said.

Mr McCormack did not say what measures the Americans might seek, but suggested that the row was coming to a head. "Frankly, the patience of the international community is not infinite on this issue because it’s a serious issue," he said.

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