US secretary of state Hillary Clinton today urged the Iranian government to help determine the whereabouts of three missing Americans and "return them as quickly as possible."
Mrs Clinton said the US did not yet have official confirmation that the Iranian government was holding the three tourists, who were reported to have crossed into Iran from Iraq while hiking in the mountains.
"Obviously we are concerned," Mrs Clinton told reporters in Washington. "We want this matter brought to a resolution as soon as possible and we call on the Iranian government to help us determine the whereabouts of the three missing Americans and return them as quickly as possible."
She said the United States, which does not have diplomatic ties with Iran, had asked Switzerland to seek information from Tehran about the missing US citizens.
The Americans were arrested after entering Iran, a source told Iran's state-run Al-Alam Arabic language television station on Saturday.
A Kurdish official said the group, believed to be two men and a woman, did not know the area and must have entered the Iranian side without realising it.