Washington ? The Obama administration denied on Monday that an American man sentenced to death in Iran was a CIA spy, and sharply criticized the Islamic republic in Tehran for what it called a pattern of arresting innocent people for political reasons.

White House spokesman Tommy Vietor said officials were still trying to learn the details of the sentence against Amir Mirzaei Hekmati. If true, the U.S. would condemn the verdict, he said.

Iran charged that Hekmati received special training and served at U.S. military bases in Iraq and Afghanistan before heading to Iran for an intelligence mission. A court convicted him of working with a hostile country, belonging to the CIA and trying to accuse Iran of involvement in terrorism, according to a state radio report Monday.

“Allegations that Mr. Hekmati either worked for, or was sent to Iran by the CIA are false,” Vietor said in a statement. “The Iranian regime has a history of falsely accusing people of being spies, of eliciting forced confessions, and of holding innocent Americans for political reasons.”

The 28-year-old former military translator was born in Arizona and graduated from high school in Michigan. His family is of Iranian origin, and Hekmati claims dual citizenship. His father, Ali, a professor at a community college in Flint, Mich., has said his son was visiting his grandmothers in Iran.

State Department spokeswoman Victoria Nuland called the charges against Hekmati a fabrication and demanded his release.

The White House said the U.S. would work with its diplomatic partners “to convey our condemnation to the Iranian government.”

Swiss diplomats, acting on behalf of the United States because Washington and Tehran don’t have diplomatic relations, have tried unsuccessfully to gain consular access to Hekmati. Iran doesn’t recognize dual citizenship and considers Americans of Iranian origin to be solely citizens of the Islamic republic.

For that reason, the State Department has warned U.S. citizens of Iranian background to avoid visiting the country because of “the risk of being targeted by authorities.”

“Iranian authorities have detained and harassed U.S. citizens of Iranian origin,” the department says in its Iran travel warning.

Behnaz Hekmati, Amir’s mother, said in an email to The Associated Press that she and her husband are “shocked and terrified” that their son has been sentenced to death. The verdict is “the result of a process that was neither transparent nor fair,” she said.

Her son did not engage in any acts of spying, or “‘fighting against God,” as the convicting judge has claimed in his sentence, she said. “Amir is not a criminal. His very life is being exploited for political gain.”

Hekmati’s mother said a “grave error” has been committed and that the family has authorized legal representatives to make direct contract with Iranian authorities to find a solution. “We pray that Iran will show compassion and not murder our son, Amir, a natural born American citizen, who was visiting Iran and his relatives for the first time,” she said.

The Marine Corps said Amir Nema Hekmati served between 2001 and 2005, including one deployment to Iraq in 2004 and a stint at the military language institute in Monterey, Calif. The Marine records do not indicate any deployment to Afghanistan. It was not clear why the middle name was listed differently.

The sentence against Hekmati comes amid heightened U.S.-Iranian tensions.

The Obama administration has approved new sanctions against Iran over its disputed nuclear enrichment program, specifically targeting the regime’s central bank and its ability to sell petroleum abroad, but the stronger penalties have not taken effect. Iran has responded with warnings to American vessels against entering the Strait of Hormuz, the strategic waterway that carries to market much of the oil pumped in the Middle East.

Obama approved the new penalties against Iran on New Year’s Eve, despite his administration’s fears they could lead to a spike in global oil prices or cause economic hardship on American allies in Europe and Asia that are still importing petroleum from Iran.

The measures affect foreign financial institutions doing business with Iran’s central bank by barring them from doing business in the United States. They would apply to foreign central banks as well for transactions related to petroleum.

But the sanctions won’t take effect for six months. The president also can waive them for national security reasons or if the country in question significantly reduces its purchases of Iranian oil. The State Department says it is trying to implement the law in a way that maximizes pressure on Tehran while causing minimal disruption to the U.S. and its allies.

American officials are concerned that Hekmati’s case may become a political tool for the Iranian government.

Having imposed the worst possible sentence immediately, Iran could now seek to drag the case out. In past cases Iran has held out the possibility of releasing American prisoners on humanitarian grounds, presumably in the hopes of gaining a counter-concession from Washington. September’s release of a pair of American hikers held captive by Iran for two years is the most recent example.

Associated Press writers Lolita C. Baldor, Anne Gearan and Julie Pace contributed to this report.