"I cannot name a date" as to when the crucial agreement will be signed, Alexander Rumyantsev told AFP. "We have not agreed with Iran about anything yet."

Russia is building the Islamic state's first nuclear power reactor, but says it will not begin delivering nuclear fuel needed to operate the plant until Tehran signs a deal pledging to return the spent material to Russia.

Under pressure from the United States and Israel -- which fear that Iran is developing nuclear weapons -- Russia has made the return of the spent fuel a key condition for concluding the 800 million dollar (715 million euro) project.

Speaking on the sidelines of a meeting in Moscow with US Energy Secretary Spencer Abraham, Rumyantsev said the negotiating process with Iran was "taking a long time -- these are prolonged discussions."

But he downplayed disagreements in the negotiations, which have complicated Moscow's relations with Washington on the eve of a summit later this month between Russian President Vladimir Putin and his US counterpart George W. Bush at Camp David.

"I don't see any sensation in this," he said referring to Russia's failure to sign the agreement. "This is a normal process."

"There is nothing stopping us from cooperating, but our Iranian colleagues have no experience with nuclear energy. They don't even have experience in dealing with nuclear fuel waste," Rumyantsev said later in the day.

Moscow officials say that negotiations over the Bushehr plant have broken down over Iran's demand for Russia to buy back the spent fuel.

The request is highly unusual since spent fuel in such deals is almost always sent back for free, and the Iranian demand was not part of the original Bushehr contract.

"Now they want us to buy back the material because they view it as valuable. We are ready to pay... but now we are negotiating the contract," he said.

The Bushehr plant is due to go online in 2005 and the United States has been pressing Russia strongly not to sign an accord.

It has further slapped sanctions against one Russian government-linked firm for selling sensitive military technology to Iran.

But several Russian officials Friday defended their military links with Iran and said Moscow would stop the Bushehr project only if Iran is found to be in violation of International Atomic Energy Agency (IAEA) regulations.

"Sometimes, our military cooperation with Iran is misunderstood," Russia's Deputy Defense Minister Mikhail Dmitriyev was quoted as saying by Interfax.

He said that Russia exported between 25 and 70 million dollars worth of arms annually to Iran.

"Mostly we are talking about repair work, modernizing old equipment and delivering spare parts," he said.

Meanwhile an atomic energy official told ITAR-TASS that Washington has not yet delivered evidence to Moscow that Tehran was developing a nuclear weapons program.

"Russia can stop the Bushehr project if Washington offers Moscow concrete proof that Iran is developing nuclear weapons," an unnamed atomic energy ministry official told ITAR-TASS.

Last Friday, the IAEA set an October 31 deadline for Iran to prove it is not secretly developing nuclear weapons. Russia has called on Tehran to comply with the decision.

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