The London talks were postponed Wednesday until next week to allow more time for phone discussions of what should be included in the package of incentives and penalties to be offered to Tehran, said a diplomat, requesting anonymity for the same reason.

U.S. State Department spokesman Sean McCormack declined to say Tuesday whether a light-water reactor would be offered in the package. But he insisted that Iran would be required to halt its program of enriching and reprocessing uranium on Iranian soil, saying the United States and others "do not want the Iranian regime to have the ability to master those critical pathways to a nuclear weapon."

In his speech broadcast live on state television Wednesday, Ahmadinejad said Iran "won't accept any suspension or end" to its uranium enrichment activities.

He said Iran trusted the European Union in 2003 and suspended its nuclear activities as a gesture to boost negotiations over its nuclear program, only to have the Europeans eventually demand Iran permanently halt its uranium enrichment program.

The 2003 deal called for guarantees that Iran's nuclear program wouldn't diverge from civilian ends toward producing weapons. Iran agreed to the request, but negotiations collapsed in August 2005 when the Europeans said the best guarantee was for Iran to permanently give up its uranium enrichment program.

Iran responded by resuming uranium reprocessing activities at its uranium conversion facility in Isfahan.

"We won't be bitten twice," Ahmadinejad said.

"We recommend that you not sacrifice your interests for the sake of others," he said in an apparent warning to the European Union about supporting the position advocated by the United States.

Ahmadinejad reiterated his threat to pull out of Nuclear Nonproliferation Treaty if international pressure to give up uranium enrichment continued.

"Don't force governments and nations to renounce their membership in the Nuclear Nonproliferation Treaty," he said asserting that Iran had the right to a civilian nuclear power program.

With Iran's nuclear program now before the Security Council, the Americans are at the forefront of efforts to introduce a council resolution that would demand Iran give up enrichment or else face the threat of sanctions. Washington seeks to make such a resolution militarily enforceable, something opposed by Russia and China, which continue instead to favor talks meant to persuade Tehran to compromise.

In the latest sign of persisting differences, Russian Foreign Minister Sergey Lavrov said Tuesday that Beijing and Moscow will not vote for the use of force in resolving the nuclear dispute.

In a gesture to Tehran, Lavrov also said Ahmadinejad will attend a summit next month in Shanghai, China, of leaders from Russia, China and four Central Asian nations.

"We cannot isolate Iran or exert pressure on it," Lavrov told reporters. "Far from resolving this issue of proliferation, it will make it more urgent."

A light-water reactor is considered less likely to be misused for nuclear proliferation than the heavy water facility Iran is building at the city of Arak, which ¡ª once completed by early 2009 ¡ª will produce plutonium waste.

Still, light-water reactors are not proliferation-proof, because they are fueled by enriched uranium, which can be processed to make highly enriched "weapons-grade" material for nuclear warheads.