June 2 (Bloomberg) -- Iran must respond ``within weeks'' to an international offer of incentives to abandon any nuclear weapons development, U.S. Secretary of State Condoleezza Rice said today, while Iranian President Mahmoud Ahmadinejad said his nation stands firm in seeking nuclear energy.

``We do need to have an answer and it can't be months; it really needs to be within weeks,'' Rice told NBC's ``Today'' show, referring to the proposal from the U.S., China, Russia, the U.K., France and Germany.

The package of incentives, which wasn't made public, was agreed on during a meeting of top diplomats from the six nations in Vienna yesterday. The offer gives Iran, holder of the world's second largest oil and natural gas reserves, a chance to avoid sanctions from the United Nations Security Council, said U.K. Foreign Secretary Margaret Beckett, who spoke on behalf of the six governments. All except Germany hold vetoes on the council.

An Iranian nuclear official said today that the country would not bend to demands that it abandon its push to enrich uranium for fission. ``We will accept no limitations in regards to our enrichment,'' Mohammad Saeedi, deputy head of the Atomic Energy Organization, told Iran's student news agency.

Saeedi said that accepting the U.S. offer to join talks with Iran if enrichment ends ``is almost impossible.''

`Maximum' Cooperation

Ahmadinejad, while not referring directly to the Vienna offer, said in Tehran his government had given ``maximum'' cooperation to UN nuclear inspectors, according to the official Iranian news agency. Ahmadinejad said opposition to Iran's nuclear program from Western governments was motivated by concern about access to the technology for the world's ``independent states,'' not about nuclear weapons.

U.S. National Intelligence Director John Negroponte told the British Broadcasting Corp. today that the U.S. estimates Iran could have atomic weapons within five to 10 years. Iran is ``the principal state sponsor of terrorism in the world'' and ``they are determined to develop nuclear weapons,'' he said.

Rice, in an interview with National Public Radio today, described the package of incentives and punitive actions as ``robust'' and suggested she was ready to meet with her Iranian counterpart if Iran agrees to suspend enrichment.

A U.S. State Department official, who briefed reporters yesterday, said the U.S. would like a final answer before the mid-July meeting of the Group of Eight industrial powers in St. Petersburg, Russia, where Iran is likely to be a top agenda item.

In Berlin today, German Chancellor Angela Merkel and Jordan's King Abdullah II appealed to Iran to accept the Western offer, with Merkel saying its leaders should ``use this chance and build on it.''

The government ministers in Vienna said they would not discuss details of the offer to Iran until Iranian officials had formally been handed the proposal.

Earlier Offer

An earlier European overture, backed by the U.S., had promised Iran admission to the World Trade Organization, access to airplane technologies and scientific cooperation. All of those elements were contained in a draft of the new incentives package published May 19 by Agence France-Presse.

Iran may be extended European help in building a commercial nuclear reactor, officials close to the International Atomic Energy Agency said two weeks ago.

Should those incentives fail, the other Security Council members attending the Vienna talks agreed to take effective action to counter Iran's program, according to the State Department official who briefed reporters.

Bush, Putin

The official said a conversation between President George W. Bush and Russian President Vladimir Putin on May 30 was critical in winning Russia's backing for tough measures.

Iran could face economic or diplomatic sanctions from the UN. Such sanctions would target Iranian officials and organizations rather than the Iranian people, a U.S. official said earlier this week.

Russia and China have resisted any UN measure that would include the threat of military action, an option that Bush says the U.S. won't exclude.

The U.S. will insist that Iran suspend nuclear work and that the suspension be verified by the IAEA, U.S. officials said. As part of the suspension, the U.S. expects a complete halt to all enrichment-related activities, including the testing of centrifuges even without the introduction of a gas that could be turned into a nuclear fuel, the State Department official said.

Centrifuges are used in the process of trying to raise the concentration of a uranium isotope crucial to a nuclear reaction.

To contact the reporters on this story: Janine Zacharia in Vienna at jzacharia@bloomberg.net; Jonathan Tirone in Vienna at jtirone@bloomberg.net

Last Updated: June 2, 2006 14:09 EDT