Relations between Tehran and Washington have deteriorated sharply since 2018 when US President Donald Trump exited Iran’s 2015 nuclear deal with major powers and re-imposed sanctions on Tehran that have crippled its economy.
Washington has long demanded that Iran release US citizens including Iranian-American father and son Baquer and Siamak Namazi.
Navy veteran Michael White, detained since 2018, returned home in June as part of a deal in which the United States allowed an Iranian-American physician Majid Taheri to visit Iran. White said he contracted COVID-19 while in detention.
In December 2018, Washington and Tehran worked on a prisoner exchange in which Iran freed US citizen Xiyue Wang, who had been held for three years on spying charges, and the United States freed Iranian Massoud Soleimani, who faced charges of violating US sanctions on Iran.
Tehran denies it holds people on political grounds, and has mostly accused its foreign prisoners of espionage.