US Secretary of State Mike Pompeo called Swiss Foreign Minister Ignazio Cassis on Monday to discuss the possible repatriation of US citizens being held in Iran.
Hours earlier, Tehran announced its readiness for unconditional talks on a prisoner swap with Washington.
“The secretary thanked the foreign minister for Switzerland’s continued and constructive role as our protecting power in Iran and for its assistance in repatriating US citizens from Iran and Myanmar,” the US State Department said.
Switzerland has been the protector of US interests in Iran since relations were severed in 1979, and has mediated and provided a humanitarian channel between the two.
“We have announced that without any preconditions, we are ready for a full prisoner swap and ready for talks on this matter,” Iran’s spokesman Ali Rabiei said on Sunday.
A US official told The National the release of the US prisoners "should be immediate and without conditions". The official did not say if an offer was on the table or when talks might start.
The New York Times reported last week that Tehran and Washington were negotiating a deal for the release of Michael White, an American navy veteran held by Iran, in exchange for Massoud Soleimani, an Iranian-American doctor held in the US.
Iran granted Mr White medical leave in March and his health is in jeopardy, his family said.
Iran holds at least four American prisoners and freed Princeton's Prof Xiyue Wang last year.
The US holds more than 10 Iranians in jail, some for breaching US immigration laws, acting deputy secretary of homeland security Ken Cuccinelli said on Monday.
In a rare public exchange between US and Iranian officials, Mr Cuccinelli and Iranian Foreign Ministry spokesman SA Mousavi criticised each other on Twitter.
Mr Cuccinelli said Iranian Foreign Minister Javad Zarif had stalled the prisoner swap and urged him “to put his money where his mouth is”.
Mr Zarif’s spokesman called the claim “rubbish” and accused the administration of US President Donald Trump of risking the lives of Iranian prisoners.
The rare potential exchange of prisoners comes two years after Mr Trump abandoned the nuclear deal between Iran and world powers in May 2018.
