The US has asked Iran to immediately release three American hikers detained for nearly nine months for allegedly entering the country illegally and expressed concern over the deterioration of their health."We ask the Islamic Republic of Iran to release these three Americans and allow them to go home and be reunited with their families," Secretary of State Hillary Clinton said. The three detained American hikers - are Shane Bauer, Josh Fattal and Sarah Shourd.They were held on July 31 last year for illegally entering the country from Iraq's Kurdistan region, according to Iran's state-run media. They were sent to Evin prison in Tehran."We are disturbed by the families' reports of their children's physical and emotional health," Clinton said.