Iran will launch its first nuclear power plant by late September, its nuclear agency's chief said. An important final test was recently carried out at the Bushehr reactor, Ali Akbar Salehi, the head of the Islamic state's Atomic Energy Organization, said Wednesday, according to the official IRNA news agency. The report did not say when the warm-water tests had been carried out, according to Reuters.

The nuclear reactor is a joint project with Russia and has cost upward of $1 billion. Progress has been delayed on the plant at least five times in the past 15 years.

U.S. Secretary of State Hillary Rodham Clinton has criticized Russia's plans to start up the Bushehr plant, saying in March it was "premature" without further assurances from Iran on its nuclear program, which Iran insists is peaceful and which the West believes could be the basis for creating nuclear weapons.

The United Nations Security Council last month adopted a fourth round of sanctions on Iran over its refusal to halt enrichment of uranium as part of its nuclear program. Russia is a permanent member of the Security Council.