"It is the most important anchor holding Iran to the non-proliferation regime," Lavrov said, adding that the project was running "under the full control of the International Atomic Energy Agency."

The construction of Iran's first nuclear plant was begun in 1975 by several German construction companies. They pulled out following a U.S. embargo on hi-tech supplies to Iran after the 1979 Islamic Revolution and the subsequent U.S. Embassy siege in Tehran.

Russia signed a contract with Iran to complete construction in February 1998.

The plant will be launched on August 21, the Russian Federal Atomic Energy Agency (Rosatom) said last week.

Western powers suspect Iran of seeking to build nuclear weapons under the guise of its nuclear program, which Tehran says is aimed at the peaceful generation of civilian energy.

On June 9, 2010, the UN Security Council approved a fourth round of sanctions against Iran over its nuclear program, including tougher financial controls and an expanded arms embargo, as well as an asset ban on three dozen companies and a travel freeze on individuals.

Later, the United States and the European Union imposed extra sanctions against Iran, including tougher restrictions on the energy sector and a tougher trade embargo.

The construction of the Bushehr Nuclear Power Plant has not been affected by the sanctions.