After being appointed by Iran's supreme religious leader yesterday, the populist Mr Ahmadinejad said: "I will plead for the suppression of all weapons of mass destruction."
But the Supreme Leader, Ayatollah Ali Khamenei, defended Iran's right to nuclear power in the face of international pressure, saying: "All powers, and especially the Great Satan America, should know that the Iranian people would not pay tribute to any power." His speech was punctuated by cries of "Death to America, Death to Israel" from regime officials.
The ceremony, held before Mr Ahmadinejad takes office on Saturday, came as Iran rejected an appeal from the International Atomic Energy Agency to delay the resumption of uranium processing at its Isfahan plant.
However, in a change of heart announced on state television later in the day, the outgoing chief negotiator, Hasan Rowhani, signalled that Tehran was prepared to wait until the IAEA could supervise the reopening of the facility. Following an exchange with the IAEA, he said, Iran would agree to wait until "early next week".
The three European Union countries that have been negotiating with Iran in hopes of mothballing its suspected nuclear weapons programme have warned that any resumption of uranium conversion would end that process.
In the light of the latest developments, a Foreign Office spokesman said Britain, France and Germany would "in the next 24 to 36 hours" seek an emergency meeting of the IAEA in which they would join the US in pressing for Iran to be reported to the UN Security Council for possible sanctions.
The Europeans say that the decision to resume nuclear-related activity by Iran, which suspended uranium conversion in November last year, is a breach of its previous undertakings.
The three countries are nevertheless intending to submit a package of economic and security incentives to Iran, after ignoring a series of deadlines set by Tehran. "It's a happy or unhappy coincidence" that the EU proposals would be put forward under Mr Ahmadinejad's presidency, and not that of his predecessor, a British official said.
The latest round of sabre-rattling from Iran, which has followed Mr Ahmadinejad's surprise election in June, has raised fears in the West that the Iranian regime plans a radical policy change that would result in a major international crisis. Following the departure of the reformist President Mohamad Khatami, the Iranian levers of power are now concentrated among the extremists for the first time since the fall of the Shah in 1979.
Diplomats say that Iran seems to have used Mr Ahmadinejad's election as the pretext for the breakdown in negotiations. Iran may feel it has support from the veto-holding states Russia and China on the security council, which could block any action. It also insists it has the right to uranium enrichment under the nuclear non-proliferation treaty.
Iranian conservatives accuse Europe of using talks to stall the programme, which they see as an important part of Iran's long-term development. Some also regard a collapse in the talks as inevitable and want to push the programme forward as fast as possible.
These conservatives also want to see new political and social crackdowns. But many of the voters who supported the new president were motivated by opposition to corruption and could oppose new restrictions. If Mr Ahmadinejad also fails to satisfy expectations by cutting high unemployment and inflation, he risks losing much of the support that propelled him to power.
Liberals are, however, worried by some of the names put forward as possible cabinet appointees. A former official accused of involvement in the murder of political dissidents has been proposed for the Intelligence Ministry and an editor of a hardline newspaper has been suggested as a minister for culture - responsible for censorship.
Blacksmith's son has powerful allies
Iran's new President presents himself as a man of the people, but he must now weigh the competing demands of important interest groups who helped put him in power. Mahmoud Ahmadinejad still lives in a humble suburban home in a lowly district of east Tehran, but he has already given up a battered Peugeot in favour of the armour-plated Mercedes of high office.
The blacksmith's son is seen by many of the 17 million Iranians who voted for him on 24 June as coming from outside the political establishment. They hope his government will tackle corruption and the unequal distribution of oil revenue.
But reformists and other critics say he is a close ally of the top conservative officials who have held power since the 1979 revolution. His rise to power was aided by the Basij Islamic militia and the Islamic Revolutionary Guards Corps.
Mr Ahmadinejad's own history in the Basij and revolutionary guards helped forge close alliances with the new generation of conservatives who have started taking over many bodies of state.
Some reports say that he was a special forces operative in the Iran-Iraq war and some former US embassy hostages say that he was one of the students who held them in 1979. Mr Ahmadinejad denies this.
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