A jailed American journalist charged by Iran with espionage stood trial behind closed doors and a verdict is expected within weeks, Iran's judiciary spokesman said Tuesday.

Roxana Saberi, a 31-year-old dual American-Iranian citizen, was arrested in late January and initially accused of working without press credentials. But an Iranian judge levelled a far more serious allegation against her last week, charging her with spying for the United States.

Judiciary spokesman Ali Reza Jamshidi said Saberi, who grew up in Fargo, N.D., was tried Monday in Iran's Revolutionary Court, which handles national security cases.

"Yesterday, the first trial session was held. She presented her final defence. The court will issue its verdict within the next two to three weeks," Jamshidi told reporters.

Saberi's father, who travelled to Iran in a bid to help win his daughter's release, and her lawyer could not immediately be reached Tuesday for comment.

Espionage charges 'baseless': State Department

The U.S. government has been pressing for Saberi's release, and the charges against her and news that she had been tried behind closed doors was a setback — especially at a time when U.S. President Barack Obama has expressed a willingness to talk with Iran after many years of rocky relations under the administration of former U.S. president George W. Bush.

The U.S. State Department has called the espionage charges against Saberi "baseless." U.S. Secretary of State Hillary Clinton has expressed concern about the case and called on Iran to release Saberi.

Roxana Saberi has been living in Iran for the last six years, working as a freelance reporter for organizations including National Public Radio and the British Broadcasting Corp.

An Iranian investigative judge involved in the case told Iranian state TV last week that Saberi had passed classified information to U.S. intelligence services but didn't provide further details.

Jamshidi criticized the U.S. on Tuesday for saying Saberi was innocent and calling for her release.

"That a government expresses an opinion without seeing the indictment is laughable," he told a press conference.