Roxana Saberi worked for the BBC for a few months in 2006
US Secretary of State Hillary Clinton has expressed her deep concern about the detention of an Iranian-American journalist in Iran.
Roxana Saberi, who is being held in Evin prison in the capital, Tehran, and has been accused of spying, will appear in court next week, her lawyer said.
"We are deeply concerned by the news that we are hearing," Mrs Clinton said.
Ms Saberi originally faced the less serious accusations of buying alcohol and working without a valid press card.
"I will, as will the rest of the (state) department, continue to follow this very closely and we wish for her speedy release and return to her family," said Mrs Clinton, who has appealed for the journalist to be freed on more than one occasion.
Ms Saberi's parents arrived in Tehran at the weekend and were allowed to see her for 20 minutes. According to her lawyer, they found her in good health and good spirits.
The journalist, 31, worked briefly for the BBC three years ago. She has also worked for the American public radio network NPR and the TV network Fox News.
A number of UK and US media outlets, including the BBC, have called on Iran to allow independent access to her.
Her lawyer, Abdolsamad Khorramshahi, said he could not comment on the accusation of spying as he had not been allowed to see the legal papers.