"Iran will soon sign an accord with Russia on the repatriation of nuclear waste," Iran's representative to the International Atomic Energy Agency (IAEA), Ali Akbar Salehi, told the official news agency IRNA.
"The Russians will soon start delivering nuclear fuel in accordance with the agreement," he added.
The Bushehr nuclear power plant deal is worth about 800 billion dollars to Russia.
But under pressure from the United States and Israel, which fear that Iran is developing nuclear weapons with the project's help, Russia has made the return of the spent fuel a key condition for concluding the massive project.
Russian officials had previously said that negotiations over the Bushehr plant had 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.
Salehi's comments, effectively announcing that Iran would agree to send spent fuel back, come after Iran also pledged to open up its nuclear programme to tougher International Atomic Energy Agency (IAEA) inspections and vowed "full transparency" with the Vienna-based UN nuclear watchdog.
Iran yielding to IAEA demands, which included its agreement to cease uranium enrichment, came during an unprecedented visit here by the foreign ministers of Britain, France and Germany.