Rosatom chief Sergei Kiriyenko on Thursday called the construction of Iran's Bushehr nuclear power plant a "big international project" in which more than 10 European Union and Asia-Pacific countries took part in the Moscow-led project.
The state-run nuclear holding had not previously mentioned having foreign help constructing the controversial plant, which Russia first agreed to finish building in 1992.
The $1 billion project has been stalled repeatedly amid international sanctions and what Tehran has called Moscow's pandering to the West.
Russian political leaders have defended the pace of the work as Rosatom seeks to gain a larger foothold in the lucrative and highly competitive market for nuclear power construction deals.
Kiriyenko will join Iranian Vice President Ali Akbar Salehi, who heads the country's Atomic Energy Organization, to open the facility on Saturday after almost four decades of sporadic work.
Inspectors from the United Nation's International Atomic Energy Agency will also be on hand to open the nuclear fuel containers and oversee their transportation to the reactor, Kiriyenko said in a meeting with Prime Minister Vladimir Putin.
The launch "coincides with Russia's position that any country in the world has the right to nuclear energy for peaceful use," provided that it is monitored by the IAEA, he said in comments carried on the government web site.
"It is also important that this is a big international program because, yes, Russia, of course, did the bulk of the work, but supplies were made from more than 10 countries, including many from the EU and the Asia-Pacific region," Kiriyenko said, without naming the countries.
A Rosatom spokesman could not be reached to comment on foreign participation in the Bushehr project. A spokeswoman for Atomstroiexport, the Rosatom unit that specializes in construction of nuclear power facilities abroad, was also unavailable for comment.
Analysts said Kiriyenko was likely overstating the extent of the foreign contributions, particularly amid pressure from Washington to hold off on starting the facility.
Construction on Bushehr started in 1974 by Kraftwerk Union, which was formed after Siemens and AEG merged their nuclear power businesses.
Siemens pulled out of the country in 1980, and a spokesman declined to comment on the project Thursday.
"Contrary to what some commentators might have suggested, this project does not pose much of a proliferation threat, because Russia has agreed to take back the spent fuel as soon as it is cool enough," said Mark Fitzpatrick, director of the Non-Proliferation and Disarmament Program at the International Institute for Strategic Studies.
"Criticism of Bushehr distracts from the real proliferation risks posed by Iran's uranium enrichment program," he told The Moscow Times.
While the Bushehr launch is unlikely to damage U.S.-Russian relations, it may do some harm to President Barack Obama domestically, Fitzpatrick said. "Conservative Republicans are looking for an opportunity, however small, to attack President Obama, and the launch of Bushehr might be used as an excuse to do that."