"We are deeply concerned about reports that US citizens Siamak Namazi and Baquer Namazi have each been sentenced to 10 years in prison," State Department spokesman Mark Toner said in a statement.
"We join recent calls by international organizations and UN human rights experts for the immediate release of all US citizens unjustly detained in Iran, including Siamak and Baquer Namazi, so that they can return to their families."
Siamak Namazi, a well-connected business consultant who has supported reformist politicians in Iran, was arrested as he arrived in Tehran a year ago.