Tehran, Iran ? Iran and Russia said Sunday they were close to finalizing a long-delayed protocol on returning spent nuclear fuel to Russia, paving the way for the launch of a Russian-built nuclear power plant in southern Iran in 2006.

Russia has said it would not ship nuclear fuel to Iran until both countries sign an agreement under which all spent fuel would be returned to Russia. The agreement is intended to prevent Iran from using spent fuel to make nuclear weapons.

“The agreement on returning spent nuclear fuel is in the final stage,” Russia’s Foreign Minister, Sergei Lavrov, told reporters in Tehran. “I think it will be signed soon.”

The signing has been delayed repeatedly by what both countries say are mainly financial details. Iran says it doesn’t have facilities to store the spent fuel. Moscow wants to pay in order to take back the fuel to Russia.

The fuel agreement will pave the way for the inauguration in 2006 of Iran’s first light-water 1,000-megawatt nuclear reactor being built by Russia in Bushehr, southern Iran.

The $800 million Bushehr contract has drawn years of protests from the United States, which says the project could help Tehran build nuclear weapons.

Lavrov, who arrived Sunday on an official visit, also called on Iran to implement a demand from the International Atomic Energy Agency, the U.N. nuclear watchdog, that it freeze all work on uranium enrichment activities, including uranium reprocessing, a technology that can be to produce nuclear fuel or nuclear weapons.

“The IAEA board has called on Iran to suspend all uranium enrichment activities voluntarily, not as an obligation,” he said. “This is to the interests of Iran and all that Tehran responds positively to IAEA.”

But Iranian counterpart Kamal Kharrazi swiftly rejected the call.