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Russia and Iran signed a deal Sunday that would deliver nuclear fuel to the Middle East country for the startup of its first reactor — a project the United States had for years pushed Moscow to drop, claiming Iran is trying to build a nuclear bomb.

Iranian Vice President Gholamreza Aghazadeh (search) and Russian Atomic Energy Agency (search) chief Alexander Rumyantsev signed the agreement at the Bushehr nuclear power plant. The signing, which was delayed by a day, came after the two senior officials toured the $800 million complex.

"Today, a very important development occurred, and that was the protocol on returning nuclear fuel, which we signed together. In the next few weeks many Russian technicians will arrive in Bushehr" to finish the plant, Rumyantsev said after the signing.

Both officials refused to discuss the details of shipping the nuclear fuel to Iran and the spent fuel back to Russia, but insisted that the agreement conforms to international nuclear regulations.

"Iran observes all the regulations on the prohibition of the spread of nuclear weapons," Rumyantsev said.

Russia, which helped build the plant, has agreed to provide the fuel needed to run it — but only if Iran returns the spent fuel to prevent any possibility Tehran would extract plutonium from it to make atomic bombs. Tehran has agreed to return the spent fuel, but the sides disagreed on who should pay for its return.

Both officials said Sunday they had agreed on details of the shipment, but said the timing and the costs — including who would pay for what — were confidential.

The signing came a few days after a summit between President Bush and Russian President Vladimir Putin (search) in Slovakia, which touched on American concerns over Russian support for Iran's nuclear program.

Washington accuses Tehran of covertly trying to build a nuclear bomb, which Iran denies. Putin has said he is sure Iran's intentions are merely to generate energy, not create weapons, and that Russian cooperation with Tehran would continue.

It wasn't immediately clear whether Thursday's Bush-Putin summit had delayed the signing, which had been expected Saturday, but Mohammad Saeedi, deputy head of Iran's Atomic Energy Organization said "the Bush-Putin talks did not have an effect on the agreement. Our talks (with the Russians) have been successful."

Just ahead of the signing, Aghazadeh showed Rumyantsev Bushehr's nuclear fuel storage house and the reactor core, expected to be operational by late 2005 or early 2006.

"What I saw was much better and more than I had expected. Assembling operations in the past three to four months have been expedited," Rumyantsev said. Referring to the process to complete the plant, he added: "I can't say the situation is excellent, but it's very good."

Aghazadeh said the fuel storage area was built to international standards. "This storage house is ready to receive nuclear fuel," he said.

Iranian efforts to produce its own fuel rather than importing it have been a bigger concern in the international community than the deal with Russia. That's because the enrichment process can be carried further to produce material for nuclear weapons.

France, Britain and Germany are trying to secure an Iranian commitment to scrap enrichment plans in exchange for economic aid, technical support and backing for Tehran's efforts to join mainstream international organizations. Iran has suspended enrichment-related activities during the talks with the Europeans, which both sides have said were difficult, but insists the freeze will be brief.

Bush has expressed support for the European efforts. But documents being circulated among International Atomic Energy Agency board members in Vienna ahead of a board meeting Monday, and seen by The Associated Press there, indicated Washington would try to increase pressure on Tehran by the next agency board meeting in June should the European talks fail.