MOSCOW, June 27: Russia's top nuclear official vowed on Sunday to avoid any further delays in the launch of a Russian-built atomic reactor in Iran by speeding up talks with Tehran on a key bilateral deal.

Russia, under strong US pressure to ditch the project, has promised to sign a special agreement with Iran obliging it to return spent fuel from the reactor to Moscow to ease concerns Tehran could extract plutonium and make nuclear bombs.

But the document's signing has been delayed repeatedly, raising speculation that Moscow could bend to US pressure and shelve the $800 million project.

"We don't face any difficulties with signing of the deal on the return on nuclear fuel from the Bushehr nuclear plant," said Alexander Rumyantsev, head of the Russian Atomic Energy Agency.

"Our Iranian colleagues have confirmed they are ready to sign this document... We will speed up talks if we see the process is being delayed because we need to fulfil our contractual obligations."

Washington has branded Iran part of an "axis of evil" of states seeking weapons of mass destruction and fears Iran would use Bushehr as a cover for the transfer of other sensitive nuclear technology.

Both Russia and Iran say Tehran could not make a nuclear bomb with the technology Moscow has been providing.

Industry insiders say disagreement over technical matters between Russia and Iran, as well as Moscow's efforts to avoid spoiling relations with the United States nearly prompted Moscow and Tehran to abandon the project earlier this year.

Speaking alongside UN nuclear watchdog head Mohamed ElBaradei, Rumyantsev said Iran was simply taking time to study ways to "optimise costs" in the return of spent nuclear fuel.

The document on the fuel's return must be signed soon for Bushehr's first 1,000-megawatt reactor to go onstream in late 2005 and reach full capacity in 2006.

Once the agreement is signed, Russia will ship fuel to Iran to start up Bushehr. Spent fuel will be sent back to a storage centre in Siberia after roughly a decade of use.

Mr ElBaradei said the International Atomic Energy Agency was closely watching Bushehr.-Reuters