The landmark agreement is sure to add to tension at the meeting of the International Atomic Energy Agency's (IAEA) 35-nation board of governors as the United States charges that Tehran is using its civilian program to hide development of nuclear weapons.

Under the deal, which would cap an 800-million-dollar contract to build and bring the Bushehr nuclear power plant on line, Russia will fuel the reactor on condition that Iran sends back spent fuel, which could potentially be upgraded to weapons use.

The condition that spent fuel be returned was built into the deal as a concession to Western concerns.

Russia's top atomic energy official Alexander Rumyantsev said the plant would go online at the end of 2006.

Despite this shock announcement, the IAEA board is not expected either to condemn Iran or to give it a clean bill of nuclear health at this week's meeting at the agency's headquarters in Vienna.

The United States would like to see the IAEA bring Iran before the UN Security Council for possible sanctions but has little backing for this on the board.

Iran meanwhile, which seeks to legitimize its nuclear program, would like to see the IAEA drop its two-year-old inquest into this program and certify that Tehran's atomic intentions are strictly peaceful but the IAEA will continue to investigate, diplomats said.

In addition, Britain, France and Germany, which are holding talks on behalf of the European Union with Iran, want more time to work out a deal for Tehran to abandon uranium enrichment, the key part of the nuclear fuel cycle, in return for trade and regional security benefits.

All this leaves room for political maneuvering, with the crunch time possibly coming at the next IAEA board meeting in June.

For the first time in seven board meetings since June 2003, IAEA chief Mohamed ElBaradei will not be submitting a written report on Iran, as he feels he has no major revelations after releasing a comprehensive report last November.

The November report documented almost two decades of hidden Iranian activity "to master an independent nuclear fuel cycle" but ElBaradei said "the jury is still out" on whether Iran is trying to develop atomic weapons.

ElBaradei will be reporting orally to the board on Monday and will say that Iran has not yet allowed IAEA experts to follow up on inspections of Iran's Parchin military facility, where Washington charges Tehran is simulating testing of atomic weapons, diplomats said.

The IAEA is also looking into other new matters, such as tunnels being built that could hide nuclear material or equipment, and has still not resolved two lingering major questions -- that of Iran's research into sophisticated centrifuges to do enrichment and highly enriched uranium contamination found in Iran, according to the diplomats.

US President George W. Bush said last week in Bratislava, where he held a summit with Russian President Vladimir Putin, that he was hopeful a diplomatic solution can be reached over Iran's nuclear program.

But at the same time, US diplomats in Vienna were circulating a three-page statement to IAEA board members saying that ElBaradei should file a report on Iran ahead of the June board meeting in order to force a decision on Tehran's nuclear program, a European diplomat who asked not to be named told AFP.

The diplomat said the US efforts in Vienna were, unlike Bush's comments in Bratislava, confrontational and "not helpful" to the EU-Iran negotiations which seek a diplomatic solution.

The EU-Iran talks are deadlocked, with Iran refusing the key European demand that it permanently abandon uranium enrichment.

The IAEA board will also consider the question of the election of a new IAEA director general but the vote is expected to be put off to June since the United States opposes ElBaradei's re-election but almost all other board members support him.

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