Iran's Foreign Minister Mohammad Javad Zarif signaled his country's full willingness for a "comprehensive prisoner exchange" with the United States. Zarif made the announcement on his Twitter account Dec. 9, only two days after the Islamic Republic and the United States swapped prisoners in a deal facilitated by the Swiss government, which acts as a neutral intermediary in the absence of formal US-Iran diplomatic ties.
For a long time now, Washington and Tehran have been trading accusations of holding the other side's nationals on a merely political agenda with no solid legal grounds. Suggesting the same, Zarif's tweet described freed Iranian prisoner Masoud Soleimani as a "hostage." A high-profile stem cell scientist, Soleimani was arrested on a research visit to the United States last October. He was formally charged with trying to sidestep US sanctions on Iran in his attempt to import to his home country "growth factors" — proteins used for cell culturing and specifically employed in Soleimani's area of expertise.