The 1,000 megawatt reactor is located in the southwestern Iranian city of Bushehr, a port town on the Persian Gulf. Construction of the reactor began in the 1970s and is near completion.
Built and designed by Russian engineers, the facility is worth $800 million. Nuclear fuel for the reactor is also produced by Russians and is awaiting delivery. The U.S. is pressuring Russia to halt nuclear cooperation with Iran, but Russia has already built the reactor and signed a fuel deal.
For years, Iran kept its nuclear activities under wraps, so its unprecedented openness comes as a surprise to U.S. officials, who remain wary. The United States insists the civilian nuclear program is being used as a guise for weapons development.
White House Press Secretary Scott McClellan says one tour does not change things. "Iran is pursuing a nuclear weapons program under the cover of a civilian program. That remains a concern."
Iranian officials say they have no intention of producing nuclear weapons, and that the Bushehr site is under the scrutiny of the United Nations' nuclear watchdog, the International Atomic Energy Agency.
Fear aside, former UN weapons inspector Hans Blix dismissed worries about the Bushehr reactor. Blix says this reactor, at least, is not suitable to produce weapons-grade material. Iran argues its nuclear program is crucial to meet increased energy demands from a growing population. It is in negotiations with three European countries to renounce weapons in return for incentives.
U.S. Secretary of State Condoleezza Rice called on Iran to reach an agreement. "We believe that Iran should take advantage of the opportunity that is being provided to them by the European Three to give confidence to the international community that they are prepared to live up to their international obligations not to seek a nuclear weapons program under cover of civilian nuclear power."
The U.S. has indicated it will seek United Nations sanctions against Iran if there is no agreement.