Russia held firm Thursday to its plan to sell Iran two nuclear reactors despite U.S. objections but offered a hint of compromise over a more controversial sale of a gas centrifuge capable of producing weapons-grade uranium.


As wrangling continued over the deal six days before a summit meeting between presidents Boris Yeltsin and Bill Clinton, Russian and Iranian nuclear officials denied that Moscow had signed a separate contract to sell Tehran the centrifuge.


At the same time, Foreign Ministry spokesman Grigory Karasin told a press conference that Moscow is pressing ahead with the $1 billion deal for two light-water reactors.


"Russia will not cancel its decision, even in the face of threats from foreign countries," he said.


But Karasin was more conciliatory on the gas centrifuge, which he called a "distinct" issue.


Later Thursday, an Iranian nuclear official said at the United Nations that Iran would return spent fuel from the reactors to Russia for safeguarding,The Associated Press reported.


"We don't have any use for it," said Mohammad Sadegh Ayatollahi, Iran's envoy to the International Atomic Energy Agency, the IAEA.


A U.S. official, speaking on condition of anonymity, told Reuters on Wednesday that the gas centrifuge contract had already been signed.


"Both of these deals, as we understand them, are contracts that have been signed but not fulfilled," the U.S. official said.


But Ayatollahi denied that his country was seeking to buy the gas centrifuges.


His denial followed one from Vitaly Masonov, spokesman for the Nuclear Power Ministry, also Thursday.


"Today nothing has been signed," Masonov said of the centrifuge deal. "It exists as a theme, but further than that it doesn't go."


Masonov said Russia and Iran were discussing a 10-point nuclear cooperation program and that the only part which had received a definite go-ahead was the sale of the light-water reactors.


"Only one point of the 10 themes has been signed," Masonov said. "Nothing has been done on the remaining themes. They are in the process of being worked out."


Russian Foreign Minister Andrei Kozyrev hinted in Washington last week that Nuclear Power Minister Viktor Mikhailov had acted unilaterally on the gas centrifuge deal. This appeared to suggest Russia might be willing to renegotiate it.


The U.S. official, however, told Reuters that Washington was standing firm in opposing both projects.


"We're not willing or interested in making a deal on one and not making a deal on the other," he said. "We think both of them should be turned off. We're not interested in a compromise."


Russia's nuclear trade with Iran will be one of the dominant themes at next week's U.S.-Russian summit. Clinton signed an order Sunday cutting off trade and investment to Iran, which he accuses of fostering terrorism. (Story, Page 5.)


The $1 billion deal to supply Iran with the reactors has aroused strong opposition in the United States, which is concerned that Iran will use the by-product of nuclear power stations to build atomic weapons.


Support for Washington's position came Thursday from Uzbek President Islam Karimov, who said he was opposed to the nuclear power deal with Iran, Itar-Tass reported. "I do not approve of Russia's action," he told journalists in Tashkent.


But analysts say that the gas centrifuge deal, giving Tehran the means to enrich uranium, would be potentially much more threatening.


"It is much more serious than the light-water reactors," said Andrew Pierre, a senior associate with the Carnegie Endowment for International Peace in Washington. "This could truly provide the knowledge and means to make weapons-grade material."


Hans Meyer, spokesman for the IAEA in Vienna, said Russia was a member of the "London suppliers club," a group of nuclear-weapons nations that had drawn up a list of equipment which they had agreed not to export. He said the gas centrifuge equipment was almost certainly on the list.