State Department spokesman Philip Crowley said the meeting took place as officials sought to explain to the families "steps that we are taking to do everything possible to gain their release."
Washington, which has no diplomatic relations with Tehran, has asked Austria to help in the matter, Crowley noted.
The meeting came less than a week after the families expressed concern over the health of the detainees, who have not been formally charged by Iran.
Relatives of Shane Bauer, 27, Sarah Shourd, 31, and Josh Fattal, 27, said last week that Swiss diplomats that visited the detainees for the first time in nearly five months found them weak and demoralized.
Clinton said recently that the trio had been "unjustly held for almost nine months without formal charges or access to legal representation."
The three were arrested last July 31 after straying across the border during a hiking trip in Iraq's Kurdistan region. They are being held in Tehran's Evin prison.
Iranian Intelligence Minister Heydar Moslehi has accused the hikers of cooperating with "intelligence services," without elaborating. He said Iran had "compelling evidence" of the ties.
In mid-December, Foreign Minister Manouchehr Mottaki said Iran would put the Americans on trial after they "illegally" entered the country.
