JEFFREY BROWN: There were grave new developments today in Iran's war of wills with the West, and with the U.S. in particular. One involved the regime's nuclear program, the other an American condemned to death.
Margaret Warner has our report.
MARGARET WARNER: Amid cries of "Death to America" today, the Iranian supreme leader, Ayatollah Ali Khamenei, was defiant at a Tehran rally. He proclaimed his nation would not give up its nuclear program, despite the economic damage done by international sanctions.
AYATOLLAH ALI KHAMENEI, supreme leader of Iran (through translator): The strong decision of the sacred Islamic republic is based on not being diverted from the path it has adopted, not surrendering, and resisting against bullying and extreme demands of superpowers.
MARGARET WARNER: Khamenei's declaration came as the International Atomic Agency in an email to Reuters said Iran has begun enriching uranium at a second underground site. Iran had announced its intention to do so on Saturday.
The existence of the facility at Fordow, near the Iranian holy city of Qom, was publicly revealed by Washington and its allies in late 2009. It is very deep underground, unlike a similar plant at Natanz.
The Iranian government insists that its nuclear activities are for peaceful energy purposes only, an assertion disputed by the U.S. and its allies. On CBS yesterday, Secretary of Defense Leon Panetta repeated international demands that Iran stop enriching uranium.
SECRETARY OF DEFENSE LEON PANETTA: But we know that they're trying to develop a nuclear capability, and that's what concerns us. And our red line to Iran is, do not develop a nuclear weapon. That's a red line for us. They need to know that, if they take that step, that they're going to get stopped.
MARGARET WARNER: Tensions between the U.S. and Iran had already been heightened last week, as President Obama signed new sanctions legislation and the Iranians issued threats against American warships transiting the Straight of Hormuz.
The waterway is a vital Persian Gulf choke point for oil shipping. And today the tensions were stoked further by this announcement.
MAN: Iran has sentenced to death a detained U.S.-born Iranian man charged with spying for the U.S. intelligence agency, the CIA.
MARGARET WARNER: Amir Mirzaei Hekmati is a former U.S. Marine and military translator. Born in Arizona to a family of Iranian descent, he is said to hold dual citizenship. He was detained in Iran last August and tried for espionage last month.
The verdict was reported today. In Washington, White House spokesman Jay Carney rejected the charges and the death sentence.
JAY CARNEY, White House press secretary: If true, we strongly condemn such a verdict and will work with our partners to convey our condemnation to the Iranian government. Allegations that Mr. Hekmati either worked for or was sent to Iran by the CIA are false. The Iranian regime has a history, as you know, of falsely accusing people of being spies, of eliciting forced confessions.
MARGARET WARNER: Amid the charges and countercharges, there was one episode of goodwill involving the U.S. and Iran. Late Thursday an American destroyer, the USS Kidd, rescued 13 Iranian fishermen and their vessel from Somali pirates in the Gulf of Oman just outside the Persian Gulf. The Kidd is part of the battlegroup around the aircraft carrier John C. Stennis, a ship that left the Gulf just days earlier and that Iran had warned not to return.