"We are deeply concerned by the news we are hearing," Clinton told reporters when asked about reports that Iran had charged Saberi with spying.
She said the State Department had asked Swiss interlocutors to get the "most accurate, up-to-date" information about the case. Switzerland represents U.S. interests in Iran as Washington and Tehran do not have diplomatic ties.
"I will, as will the rest of the department, continue to follow this very closely and we wish for her speedy release and return to her family," added Clinton, who has urged Saberi's release personally on several occasions.
In a break from usual diplomatic procedures, Clinton's staff handed over an aide-memoire to an Iranian delegation attending a conference in the Hague last week, urging help in Saberi's case and that of two other Americans.
Saberi's case comes as Washington is looking for ways to engage Iran on a series of issues from Afghanistan to Iraq and Tehran's nuclear program, which the West says is aimed at building an atomic bomb.
Iran's ISNA news agency, quoting a judge who is the deputy head of Iran's prosecutor's office, said Saberi had been charged with espionage and had "accepted" the accusation.
Saberi, a 31-year-old Iranian-American freelance journalist born in the United States, has reported for the BBC, NPR and other media. She was arrested in late January for working in the Islamic Republic after her press credentials had expired.
(Reporting by Sue Pleming, editing by Anthony Boadle)
