The head of the U.N. atomic watchdog agency told a 35-nation meeting Monday he had made little progress in his probe of suspicious aspects of Iran's nuclear program.

The International Atomic Energy Agency "has not made much progress in resolving outstanding verification issues," Mohamed ElBaradei told board member nations, alluding to suspicions that some of Tehran's nuclear activities could be used to develop bombs.

The United States and Europe are lobbying other nations at the meeting to join them in urging Iran to accept a package of rewards for freezing uranium enrichment — and in warning Tehran of U.N. Security Council action if it refuses, according to documents shared with The Associated Press.

Chief U.S. delegate Gregory L. Schulte called on Iran to respond positively to demands that it negotiate and suspend enrichment, a process that can make nuclear fuel for a power plant or fissile material for an atomic bomb.

"The next decision needs to be taken not in Vienna but in Tehran," he said.

Iran insisted again Monday it had a right to uranium enrichment, expressing reluctance to suspend it as a condition for negotiations over the incentives offered by the five permanent U.N. Security Council members — the United States, Britain, China, France and Russia — plus Germany.

CountryWatch: Iran

Iranian spokesman Gholam Hossein Elham would not say whether the Islamic republic would suspend enrichment for negotiations, instead repeating the government line that enrichment was Iran's "obvious right."

"This is a nonnegotiable issue," Elham said.

Iran has not responded formally to the incentives but said Sunday that parts of the package were acceptable, others were not, and the key issue of enrichment needed clarification.

Elham gave no indication of when Iran would reply to the package presented June 6. In Luxembourg, European Union foreign policy chief Javier Solana said he expected an Iranian response this week.

Meanwhile, Israeli Premier Ehud Olmert said in London that his country would not accept a nuclear-armed Iran. Iranian President Mahmoud Ahmadinejad repeatedly has questioned Israel's right to exist and said in October the Jewish state should be "wiped off the map."

Israel is believed to possess the world's sixth-largest nuclear arsenal. Olmert sidestepped a question on whether Israel would act alone against Iran's nuclear program — as it did when Israeli warplanes destroyed Iraq's Osirak nuclear facility in 1981.

Diplomats briefed on the six-nation offer told the AP it demands an enrichment freeze that would last years beyond the conclusion of any successful negotiations with Iran.

Long-term, verifiable suspension of enrichment is a "red line" for the United States and its key Western allies, one diplomat said.

Still, the diplomats spoke of potential divisions on enrichment among the six powers. They spoke on condition of anonymity because the negotiations were confidential.

China, Russia and potentially Germany may be prepared to allow Iran some tightly controlled small-scale enrichment rather than to see negotiations founder. Additionally, Russia and China might balk at enforcing the potential penalties: selective U.N. sanctions imposed on Iranian officials and activities.

One of the diplomats said U.S. and European lobbying efforts were chiefly aimed at influential members of the Nonaligned Movement — countries such as India, Egypt, Argentina and Brazil that carry great weight among other bloc members and have broken ranks to support Iran's referral to the Security Council.

The Nonaligned Movement, the world's biggest bloc after the United Nations, has emphatically backed Iran.