UNITED NATIONS - The world's most powerful nations failed to agree on new sanctions against Iran amid reports that Iranian President Mahmoud Ahmadinejad wants to put Tehran's case for a nuclear program before the UN Security Council.

Syrian president Bashar Assad, right, meets with Iranian defense minister Mostafa Najjar in Damascus on Sunday March 11, 2007. [AP]

The surprise announcement about Ahmadinejad's intention to fly to New York came in the throes of intense debate Sunday among the five veto-wielding permanent council members - the US, Russia, China, Britain and France - and Germany on additional measures to pressure Iran to suspend uranium enrichment.

South Africa's UN Ambassador Dumisani Kumalo, whose country holds the rotating Security Council presidency, said Ahmadinejad had not made a formal request to address the UN's most powerful body, but if he did, "it would be very difficult to deny him that opportunity."

Kumalo said he would "be open to consulting" with the other council members on scheduling Ahmadinejad's appearance. "I would be surprised if they said they don't want to hear him," he told The Associated Press.

Whether an appearance before the Security Council by Ahmadinejad would affect the contents or vote on a new UN resolution remains to be seen.

Iranian TV on Sunday quoted government spokesman Gholam Hossein Elham as saying Ahmadinejad "intends to attend a UN Security Council meeting to be held on Iran's nuclear case in order to defend the rights of the Iranian nation in exploiting peaceful nuclear energy."

The announcement came hours before ambassadors of the six key nations met for the fifth time in a week to discuss what additional sanctions to include in a new resolution.

In December, the Security Council imposed limited sanctions against Iran for its refusal to freeze uranium enrichment. It ordered all countries to stop supplying Iran with materials and technology that could contribute to its nuclear and missile programs, and to freeze assets of 10 key Iranian companies and 12 individuals related to those programs.

The council warned it would adopt further nonmilitary sanctions if Iran refused to comply.

Iran not only refused to suspend its enrichment program but expanded it. So the six key nations that have been trying to rein in Iran's nuclear program started discussing possible new sanctions including a travel ban, an arms embargo, trade restrictions, and an expanded list of people and companies subject to an asset freeze.

After Sunday's 1 1/2-hour meeting at Britain's UN Mission, however, it was clear that the key players remain divided. The US and Europe want tougher sanctions than Russia and China, which both have strong business ties with Iran, are prepared to accept.

China's UN Ambassador Wang Guangya said the basic positions of the six countries remained the same "so I feel now it's up to our capitals to have one more round of exercises before we can meet again."

He said it would take "at least a couple of days" before the permanent members come up with a draft resolution to circulate to the 10 nonpermanent council members. The full council would then need time to consider the draft before it was put to a vote.

Russia's UN Ambassador Vitaly Churkin said negotiations were "moving slowly, back and forth." Asked whether the six were any closer to agreement, he said, "Maybe a little bit, a little bit - but very, very gradual."

Acting US ambassador Alejandro Wolff said Sunday's session "was a difficult one."

"As always, when you get down to the last bits of agreement, the discussions harden a bit," he said. "We had a session today that showed that there were still some firm views on all sides... I am hopeful still that we can overcome these remaining differences."

France's UN Ambassador Jean-Marc de La Sabliere said the negotiations "are moving in the right direction."

"We are not yet there but ... I expect, I hope that we will be able to have this resolution adopted next week," he said.

China has resisted proposed cutbacks on loan guarantees for companies doing business in Iran, a measure strongly supported by the United States.

There has been less friction over a proposal to ban Iran from exporting arms, although China wants the banned weapons to be specifically defined.

As for Ahmadinejad, the Security Council would have to consider any request for him to speak, but approval seems likely.

"I think that any member can have the right to come to the council if they wish," said China's Wang who then added with a laugh: "It will be fun if he comes - especially in connection with the adoption of this resolution!"

Wolff, the US ambassador, said he had only seen news reports and would wait for a formal request to the council.

"I've not seen any request for a visa," he said. "I've not seen anything concrete, so I don't know what to make of it."