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 stunning election victory in June.

In his first address, the new president 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 progra-mme.

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

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

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

Mohammad Khatami.

The European Union and United States on Tuesday issued sharp warnings to Tehran over its threats to resume some sensitive nuclear fuel work, risking an international crisis.

But shortly after the new president took office Iran's nuclear negotiator Ali Agha Mohammadi said the country hoped to resume limited nuclear activities at a uranium conversion facility on Wednesday despite the risks of triggering an international crisis."I hope to remove the seals and resume activities today," nuclear negotiator Ali Agha Mohammadi told reporters, refering to seals placed by international nuclear inspectors on the conversion plant in the central city of Isfahan.