Russia said yesterday it would begin loading nuclear fuel into the reactor of Iran's first atomic power station on 21 August, an irreversible step marking the start-up of the Bushehr plant after nearly 40 years of delays.
Russia agreed in 1995 to build the Bushehr plant on the site of a project begun in the 1970s by the German firm Siemens, but delays have haunted the $1bn (£640m) project and diplomats say Moscow has used it as a lever in its relations with Tehran.
The United States has criticised Russia for pushing ahead with the Bushehr project at a time when major powers, including Russia, are pressing Tehran to allay fears that its nuclear energy programme may be intended for developing weapons.
But Western fears abated when Moscow reached an agreement with Iran obliging it to return spent fuel to Russia. Weapons-grade plutonium can be derived from spent fuel rods.