KERMAN, Iran (AP) — Iran's president warned the United States on Wednesday that it will miss a historic opportunity for cooperation if it turns down a nuclear fuel swap deal that Washington has dismissed as a ploy.

Differences over the deal — and the U.S. push for new sanctions over Iran's disputed nuclear program — have threatened to close the door on President Barack Obama's already fading policy of outreach to Tehran.

"There are people in the world who want to pit Mr. Obama against the Iranian nation and bring him to the point of no return, where the path to his friendship with Iran will be blocked forever," Iranian President Mahmoud Ahmadinejad said during a rally in the southern town of Kerman.

The swap offer was negotiated last week by Brazil and Turkey, which are opposed to new U.N. sanctions on Iran. The United States quickly announced that it had won agreement from the other permanent members of the Security CouncilRussia, China, Britain and France — as well as Germany on a draft resolution that would hit Iran with a fourth round of penalties for refusing to completely halt uranium enrichment.

U.S. Secretary of State Hillary Rodham Clinton on Tuesday rejected the Iranian plan to swap some of its enriched uranium for reactor fuel as a "transparent ploy" to try to avoid new sanctions.

British Foreign Office Minister Alistair Burt agreed and told a briefing for U.N. correspondents in New York on Wednesday that the Brazil-Turkey-Iran agreement "doesn't address the key issue ... for Iran to talk about its nuclear policy and nuclear issues."

At U.N. headquarters, Security Council experts were continuing work on a new list of individuals, companies and other entities that would be subject to sanctions, including a freeze of their assets and a travel ban. One U.N. diplomat familiar with the negotiations, who spoke on condition of anonymity because the discussions are private, said the sanctions resolution could be put to a vote by mid-June.

The U.S. and its allies worry that Iran is seeking to develop atomic weapons. Tehran says its nuclear program only seeks energy-producing reactors.

The hardening of positions reflects a shift in tone by Obama, who came to office promising a policy of dialogue with Iran. The effort has made little headway, with the United Nations demanding Iran halt uranium enrichment and Tehran refusing and expanding its enrichment program. The dialogue policy has also been complicated by the Iranian leadership's heavy crackdown on the opposition after June 12 presidential elections that Ahmadinejad is accused of winning by fraud.

The fuel swap deal was touted as a rare opportunity to promote cooperation. A U.N.-drafted plan put forward in October called for Iran to send the majority of its low-enriched uranium abroad for further processing into fuel rods to be returned to it for use in a research reactor. The U.S. sought the plan as a way to ensure Iran, at least temporarily, did not have enough low-enriched uranium to be further processed into a nuclear warhead.

But Tehran balked for months over the terms of the plan. The deal it finally reached with Turkey and Brazil contains many similar provisions. However, since October, Iran has accumulated enough low-enriched uranium to still build a warhead even if it sends the amount under the deal abroad, making the deal less attractive to the West. Washington has accused Iran of trying to stall.

In his speech, Ahmadinejad said Washington and its allies should take the deal if they want to show they are open to dialogue.

"If they (U.S. and its allies) are truthful when they say they seek cooperation ... they should accept this offer," Ahmadinejad said. "But if they seek excuses, they should know that the path to any interaction will be closed."

He also had unusually harsh words for Russian President Dmitry Medvedev, accusing him of caving in to U.S. pressure for new sanctions.

"Justifying the behavior of Mr. Medvedev today has become very difficult," he said. "The Iranian nation doesn't know whether (Russians) ultimately are friends, whether they stand by us or are after other things. This is not acceptable."

Moscow is a longtime trade partner of Iran with more leverage over it than Western nations.

"I hope Russian leaders and officials pay attention to these sincere words and correct themselves, and not let the Iranian nation consider them among its enemies," he said.

Russia issued a swift rebuke, saying its position was guided by long-term state interests and was "neither pro-American, nor pro-Iranian."

Russia rejects "all manifestations of unpredictability, political extremism, non-transparency and inconsistency in making decisions on issues of global importance," top presidential foreign policy adviser Sergei Prikhodko said. "No one has ever managed to save his authority by making use of political demagoguery."

Like the U.N.-backed plan, Tehran's proposal would commit Iran to shipping 2,640 pounds (1,200 kilograms) of low-enriched uranium for storage abroad — in this case to Turkey. In exchange, Iran would get the fuel rods made from 20-percent enriched uranium within one year.

While in October that amount would have been around 70 percent of Iran's low-enriched uranium, its stockpiles now are believed to have grown to around 5,500 pounds (2,500 kilograms), meaning it would still have enough to produce a warhead after the shipment abroad.

Also, Iran's insistence that even with the deal it will continue to enrich uranium to 20 percent on its own — from which it can produce weapons-grade material much more quickly than from lower levels — is an even greater problem for the West.

___

Associated Press Writer Edith M. Lederer contributed to this report from the United Nations in New York.

(This version CORRECTS other members of the Security Council.)