Iran's top nuclear negotiator said Wednesday that a Russian proposal to enrich uranium for the Islamic republic needs more work and renewed a threat that Tehran will forge ahead with the technology that can make nuclear arms if the issue is referred to the U.N. Security Council.

Ali Larijani's comments came amid quickening diplomatic negotiations ahead of a crucial Feb. 2 meeting of the International Atomic Energy Agency, the U.N. nuclear watchdog that could refer the issue to the 15-nation council, which could impose sanctions.

Larijani, who is Iran's High Council of National Security Secretary, suggested it would take time to work out details of Russia's proposal — a Western-backed compromise that could provide more oversight and ease fears that Tehran is using its pursuit of atomic power as a front for a nuclear weapons program.

Iran, which insists its program is peaceful, has welcomed Moscow's suggestion that uranium could be enriched in Russia, then returned to Iran for use in the country's reactors. But haggling has continued over the specifics.

Uranium enrichment can produce fuel for nuclear reactors to generate electricity or, if sufficiently processed, the material for nuclear warheads.

"Our view of this offer is positive, and we tried to bring the positions of the sides closer," Larijani told reporters Wednesday, a day after talks with Russian security council chief Igor Ivanov. "This plan can be perfected in the future, during further talks that will be held in February."

"There are lots of details surrounding this offer that must be must be decided — the location of the plant, the form of participation, technical cooperation," Larijani said.

Speaking to Iranian state television after returning to Tehran, Larijani said the "minds of Iran and Russia are getting closer" but more effort was needed.

Russian officials have said further talks on the proposal would be held in Russia around Feb. 16 — two weeks after the emergency IAEA board meeting in Vienna, Austria.

Larijani also said Tehran would welcome talks with European countries — though an Iranian proposal to renew talks with the European Union was recently rejected.

But he reiterated that any attempt to refer Iran to the Security Council would lead the country to move forward with a full-scale uranium enrichment program.

"If they use political pressure, if our dossier is handed over or opened in an unofficial way by the Security Council, then according to a parliament decision we are obligated to revoke the fulfillment of all moratoriums," he said. "In this situation, our actions will not be limited to research. Then we will begin industrial enrichment."

He said Tehran also would be obliged to forsake a 2003 agreement with the IAEA that gave the agency more power to inspect Iranian nuclear sites and warned of unspecified additional actions to be revealed "in due time."

Iran removed IAEA seals from equipment Jan. 10, ending a 15-month moratorium, and announced it would restart research on nuclear fuel including what it described as small-scale enrichment.

European countries believe they will have enough votes at the emergency IAEA board session next week to haul Iran before the Security Council — a move also favored by the United States — but they want broad support, especially from Russia and China. Moscow and Beijing, which have close commercial ties with Iran and wield veto power in the Security Council, are not eager to see the issue come before the powerful U.N. body.

The issue also was expected to come up Monday on the sidelines of a donors conference on Afghanistan in London, with the State Department saying Secretary of State Condoleezza Rice would use the forum to discuss Iran's nuclear program with key nations.

In Vienna, a diplomat accredited to the IAEA — who demanded anonymity because he is not authorized to discuss the planned meeting with the media — said Washington and the Europeans would use the meeting to try to persuade reluctant Russia and China to support referral.

Larijani, meanwhile, was expected to meet with top Chinese officials in Beijing Thursday.

On Wednesday, U.S. Deputy Secretary of State Robert Zoellick said he had warned Chinese officials that allowing Iran to develop nuclear weapons could threaten Beijing's crucial supplies of Middle Eastern oil.

The Russian enrichment plan presents President Vladimir Putin with an opportunity to please the West without sacrificing ties with Iran. Russia is building a reactor for Iran's first nuclear power plant.

Putin called for the creation of an international system of facilities to provide enrichment and other nuclear-cycle services to nations that want nuclear power. In televised comments Wednesday, he said Russia could establish the prototype facility on its territory.