State Department spokesman Robert Wood repeated his assessment that the charges against her are "baseless" after a spokesman for Iran's judiciary said Tuesday that a revolutionary court had started her trial.
Wood added the United States was still trying to confirm details of the case via the Swiss embassy in Tehran, which handles US interests in Iran in the absence of diplomatic relations.
"We've been very concerned about the judicial process," Wood told reporters when asked about how the trial is being carried out.
"It appears to have been quite less than transparent," he said, basing his assessment of news reports of the trial.
In Tehran, Iran's judiciary spokesman Ali Reza Jamshidi said Tuesday that the first session of the trial had been held and she "was given an opportunity to speak in the court" to argue her case.
Saberi, who has been held in the notorious Evin prison in Tehran since January, is accused of "spying for foreigners … for America," he said.
The 31-year-old dual national risks the death penalty if convicted by the court, which met in closed session on Monday.
Iran's decision to put Saberi on trial comes despite calls by US Secretary of State Hillary Clinton for her release and President Barack Obama's diplomatic overtures to Iran.
Jamshidi said the verdict was expected in a week or two.
Saberi's parents Reza and Akiko Saberi, who are in Tehran to follow her case, met her in prison on Tuesday.
