Moscow, Russia (CNN) -- Russia will start loading a nuclear reactor in Iran with fuel next week, moving the project closer to being complete, both nations said Friday.
The August 21 arrival of fuel at the Bushehr facility, which Iran says will create atomic energy but other nations fear could be used for nuclear weapons, marks a key step toward its completion, Russia said.
"This event will symbolize that the period of testing is over and the stage of physical start-up has begun," said Sergei Novikov, spokesman for Russia's Federal Atomic Energy Agency.
The head of that agency will visit Iran next week, said the semi-official Fars News Agency. A Russian group is already in Iran to make the necessary arrangements for his arrival.
The reactor in the western Iranian port city of Bushehr will be operational by the third week of September, Fars said, though Novikov said the plant will not be ready to produce energy for another six months.
"All the installations and tests are now complete and the plant is now headed for launch," said Mahmoud Jafari, head of the Bushehr plant workshop.
Russia's state-sponsored nuclear corporation has been under contract for several years to help Iran build the Bushehr reactor site.
The United States has urged Russia to wait, saying more evidence is needed that Iran doesn't plan to use the site to make weapons.
Novikov said the fuel's arrival and loading into the plant will be monitored by the International Atomic Energy Agency.
"The IAEA inspectors will remove seals from containers with nuclear fuel, examine it," he said. "The fuel will be then transferred into a special storage facility. And when the Iranian nuclear watchdog agency gives its permission, the fuel will be loaded into the reactor."
Western corporations began the Bushehr facility in the 1970s but after the Iranian revolutions, the Islamic regime looked to Russia to complete the $800 million nuclear facility.
Iran has maintained all along that the site will produce energy, but the United States and other international observers remain unconvinced.
Earlier this month, the United States extended sanctions against Iran, saying it was targeting a number of Iranian businesses and groups accused of helping organizations such as Hezbollah, Hamas and the Taliban.
In June, the U.S. Treasury Department announced sanctions targeting the country's nuclear and missile programs -- identifying more than 20 companies and several individuals allegedly involved with those programs.
CNN's Max Tkachenko contributed to this report.