Ahmadinejad, 49, an ultra-conservative former revolutionary guard, was formally installed at a ceremony led by supreme leader Ayatollah Ali Khamenei after coming from nowhere to win a landslide victory in June.

In his first address as president, Amhadinejad appealed for an end to weapons of mass destruction in the world, a day after the West issued sharp warnings to Tehran over its threatened violation of a deal suspending its nuclear programme.

But shortly after the ceremony nuclear negotiator Ali Agha Mohammadi said Tehran hoped to resume uranium conversion work on Wednesday.

"I hope to remove the seals and resume activities today," Agha Mohammadi told reporters, referring to seals placed by international nuclear inspectors on the conversion plant in central Isfahan city.

The European Union and United States on Tuesday issued sharp warnings to Tehran over its threats to resume the sensitive nuclear fuel work, a move that could risk Iran being hauled before the UN Security Council for possible sanctions.

Iran had told the International Atomic Energy Agency on Monday it planned imminently to resume uranium ore conversion, the first step in the cycle to producing fuel for nuclear reactors, and not wait for a package of trade and other incentives the EU plans to present to Tehran this coming Sunday.

Khamenei, after formally endorsing Ahmadinejad as president, ordered the new government not give up "the rights of the nation."

"I congratulate the Iranian people for their vote, I confirm that vote and name Mr. Ahmadinejad president of the Islamic Republic of Iran," he said in a declaration read by former reformist president Mohammad Khatami.

"Iranian leaders have no right to give up the nation's economic and political rights. These rights must be defended," said the speech punctuated by cries of "Death to America, Death to Israel" from regime officials.

In his address, Ahmadinejad said: "I will plead for the suppression of all weapons of mass destruction.

"As servant of the Iranian nation, I want to defend its independence, our national interests and the religion of Islam. I want to defend the interests of citizens both inside and outside the country," he said.

It was the first indication from Ahmadinejad of how Iran will look under his rule. The first non-cleric to hold the post since 1981, he is Iran's sixth president since the revolution and will serve a four-year term.

Branded by his enemies before his June 24 victory as a dangerous extremist, the former Tehran mayor has gone out of his way to vow there will be "no place for extremism" in his government.

Ahmadinejad has pledged to extend "the hand of friendship" to the international community, and made clear that he is ready to work with any country that does not show animosity to Iran.

But many diplomats and rights groups doubt he will show more conciliation with dissidents or the international community than did the previous administration of Khatami, whose efforts at reform were stymied by hardliners.

Any thoughts a rapprochement with arch enemy the United States could be on the horizon have already been buried by Ahmadinejad's assertion Iran is strong enough without Washington along with accusations he took part in the 1979 kidnapping siege at the US embassy in Tehran.

But what reaped Ahmadinejad 61.69 percent of the votes in his crushing run-off win against regime veteran Akbar Hashemi Rafsanjani was his success in convincing Iranians he is an honest Muslim who cares about their economic problems.

Iranians who are more concerned with their weekly pay packets than freedom of the press will be looking to the man who proudly presents himself as the "nation's street sweeper" to put money into their pockets.

He may be helped by a bumper oil revenues in the current financial year -- 24.4 billion dollars more than budgeted -- thanks to the current high oil prices.

Having initially alarmed economic observers by promising to thwart a "mafia" that was dominating the oil industry and promising a redistribution of wealth, Ahmadinejad has moved to calm nerves by saying that he is pro-investment.