An Iranian court has sentenced an American man to death, fueling tension between the United States and Iran.

The court convicted former U.S. Marine Amir Mirzaei Hekmati of working for the CIA.

The Iranian government accused Hekmati of receiving special training at U.S. military bases in Iraq and Afghanistan before heading to Iran for his alleged intelligence mission.

Hekmati's father said his son is not a spy and he was not working for the CIA.

The 28-year-old former military translator has family in Iran. He was visiting his grandmothers in the Islamic Republic when he was arrested.

Under Iranian law, he has 20 days to appeal.

Nuclear Developments

Meanwhile, two diplomats confirm reports that Iran has begun uranium enrichment at a new underground bunker.

They say the facility is producing material that can be upgraded quickly for use in a nuclear weapon.

They also say centrifuges at the Fordo site are churning out 20 percent uranium. That's greater than the 3.5 percent being made at Iran's main enrichment plant.

The diplomats are basing their information on an inspection last week by the International Atomic Energy Agency.

Iran's development of nuclear fuel technology has led to U.N. sanctions and accusations from Washington that the regime is trying to develop nuclear weapons.