The United States on Monday urged Iran to free an American man sentenced to death by an Iranian court on charges of spying for the U.S. Central Intelligence Agency.

The White House and State Department said allegations that Amir Mirza Hekmati, an Iranian-American dual citizen, worked for or was sent to Iran by the CIA are false.

Iran's semi-official Fars news agency said a court sentenced Hekmati to death for ties to the CIA and for cooperating with what it called a “hostile country.” In December, Iran's state television shown Hekmati making what was called a confession in Farsi and English.

White House spokesman Jay Carney said that if the reports of the death sentence are true, the Obama administration “strongly condemns” the verdict. But he declined to say what options Washington is considering beyond working through Swiss intermediaries in Tehran.

State Department spokeswoman Victoria Nuland said “this is not a new tactic on the part of the Iranian government.” She added, “we obviously dismiss the accusations and believe that any confession Hekmati may have made was clearly coerced.”

“If it is true that he has been so sentenced, we would condemn this verdict in the strongest terms, and we are working with all of our partners to convey that condemnation to the Iranian government. We have maintained from the beginning that the charges against him are a fabrication, and we call on the Iranian government to release him immediately.”

A U.S. statement said Tehran “has history of falsely accusing people of being spies, of eliciting forced confessions, and of holding innocent Americans for political reasons.”

In the video, Hekmati said he was specially trained and served at U.S. bases in Iraq and Afghanistan before being sent on a mission to infiltrate the Iranian intelligence ministry. Iranian news reports say he was detained in August or September last year.

In a statement Monday, Amnesty International said Hekmati, a 28-year-old former U.S. Marine Arabic translator, did not receive a fair trial and questioned what it called “the timing and political circumstances” of his sentencing.

The international human rights group appealed to Iran not to execute Hekmati, noting that an appeal against his conviction would have to be filed within 20 days of his sentencing.