Iran has confirmed that it is holding three Americans thought to have strayed into its territory, a top official in the US says, BBC reported.
National Security Advisor Jim Jones told NBC television that the official confirmation came on Sunday morning.
The US had sent "strong messages" to Tehran urging their release, he said.
The trio are thought to have crossed the border on 1 August while hiking in Iraq's Kurdish region. There has been confusion over their whereabouts since.
The deputy governor of Iran's Kurdistan province said on 4 August that they were being questioned, but the foreign ministry in Tehran said a day later that it could neither confirm nor deny that they were being held.
"The government has officially acknowledged they have them in their custody," Mr Jones told NBC's "Meet the Press". "That is of this morning that we have that confirmation."
"We have sent strong messages that we would like these three young people released as soon as possible," he said.
The Americans have been named by relatives as Shane Bauer, a Middle East-based freelance journalist from Minnesota, his girlfriend, Sarah Shourd, and Joshua Fattal from Pennsylvania, whose father is Iraqi.
The frontier in the area where the trio are thought to have entered Iran is said to be poorly marked.