Iran will immediately retaliate if referred to the U.N. Security Council next week by forging ahead with developing a full-scale uranium enrichment program, a senior envoy said Monday.

The comments by Ali Asghar Soltaniyeh, a senior envoy to the International Atomic Energy Agency, reflected Iran's defiance in the face of growing international pressure over its nuclear program. Enrichment can be used in electricity production but it also is needed in making uranium-based nuclear weapons.

Separately, Iran's top nuclear negotiator planned to travel to Moscow on Tuesday for a high-level session as talks intensified surrounding a proposal to have Iran's uranium enriched in Russia, then returned to Iran for use in the country's reactors — a compromise that would provide more oversight and ease tensions.

Ending a 15-month commitment, Iran removed IAEA seals from equipment Jan. 10 and announced it would restart experiments, including what it described as small-scale enrichment — a move that led key European countries to call for an emergency session of the U.N. nuclear watchdog agency's board of governors Feb. 2.

The Europeans also began drafting a basic text for a resolution calling for the Security Council to press Tehran to reimpose its total freeze on enrichment and "to extend full and prompt cooperation to the agency" in its investigation of suspect nuclear activities — though it stops short of asking the council to impose sanctions.

Soltaniyeh, in comments to The Associated Press, warned against referral, suggesting such a "hasty decision" would backfire.

Whether Iran's suspension of its full-scale enrichment program remains in effect "depends on the decision of Feb. 2," he said. Asked if that meant Iran would resume efforts to fully develop its nascent enrichment activities if the board votes for referral at that meeting, he said, "yes."

Iran insists its nuclear ambitions do not go beyond wanting to generate fuel, but concerns are growing its main focus is trying to make nuclear weapons — something more than three years of IAEA investigations have failed to prove or disprove.

IAEA chief Mohamed ElBaradei, meanwhile, rejected a request by the United States and several other member nations for a full report on the agency's investigation into Iran's nuclear program, signaling his resistance to ratcheting up pressure on Tehran.

In a letter dated Friday, Gregory L. Schulte, the chief U.S. representative to the IAEA, asked ElBaradei to prepare a written report on the "status of IAEA efforts to investigate indications of an Iranian nuclear weapons program" and on other activities Washington says are a cover for such a program. Supporting letters from the other countries also asking for a special report were dated Monday.

In a written reply dated Monday, ElBaradei said "a detailed report" would only be available in March, the next scheduled meeting of the IAEA board. Instead, he offered an "update brief" for the Feb. 2 meeting, to be read by a deputy.

The exchange in the letters, which were made available to AP, reflected differences between ElBaradei and the United States and its key allies over the handling of the Iran nuclear issue.

Diplomats close to the agency — who demanded anonymity for divulging confidential information — said the IAEA chief was unhappy about the push for a special board meeting and would have preferred to wait until the scheduled March session, when he hopes to end a more than three-year probe of Iran's nuclear dossier.

Iran repeatedly has said it is willing to offer guarantees that its nuclear program won't be used to manufacture weapons. But it has so far refused to give up what it calls its clear rights under the Nuclear Nonproliferation Treaty to enrich uranium and produce nuclear fuel.

In Moscow, Foreign Minister Sergey Lavrov encouraged Tehran to adopt a position that would help ease tensions.

"We count on discussing with you the so-called nuclear problem, around which the situation is currently being heightened," Lavrov said at the start of a meeting with Deputy Iranian Foreign Minister Mehdi Safari. "We hope that our Iranian friends will choose a position that helps to ease tension and renew negotiations."

Iran's top negotiator, Ali Larijani, will meet in Moscow with top Russian officials, including Russia's Security Council head Igor Ivanov, the council's press service said. Ivanov visited Iran last year.

Russia, which has veto power in the U.N. Security Council, has close ties with Tehran and is building Iran's first nuclear power reactor, but has been moving closer to the Western position on Iran and is reluctant to let the issue cause a major rift in its relations with the United States and Europe.