"We have 11 of your citizens who are illegal aliens who we have been trying to return to your country. You suddenly SAY you want them back, so how about you send a charter plane over and we’ll return all 11 at once?" Ken Cuccinelli, acting deputy secretary of the U.S. Homeland Security Department, said in Twitter posts.
He said Washington had been trying for months to return Sirous Asgari, an Iranian science professor who was acquitted in November of stealing trade secrets but was still under U.S. custody, and that Tehran was delaying the process.
Cuccinelli did not make any mention of a prisoner swap between the two countries that cut diplomatic relations 40 years ago - something Iranian sources have said was in the works.
Iranian Foreign Minister Mohammad Javad Zarif said on Monday that Tehran had been ready for a prisoner exchange for some time.
"In 2018, I announced that the Islamic Republic of Iran was ready to exchange all American prisoners in Iran with all Iranians imprisoned in the United States or in other countries under U.S. pressure,” Iran’s Tasnim news agency quoted Zarif as saying on Monday.
"This is what we have been saying since then. The Americans have not responded to us yet."
Both countries have called for the release of prisoners because of the novel coronavirus outbreak. Iran is the worst-hit country in the Middle East, while the United States has reported the highest number of deaths and infections worldwide from the virus.
Reuters reported last week that the United States was expected to deport Asgari, who tested positive for the coronavirus more than two weeks ago, once he received medical clearance to travel.
Iranian sources have said talks for a prisoner swap between the United States and Iran have been in the works for some time and that Washington was negotiating for the release of Michael White, a U.S. Navy veteran who has been detained in Iran since 2018. He was released from prison in mid-March on medical furlough but remains in Iran.
It was not immediately clear who would be exchanged for White, but a U.S. official denied that Washington was negotiating to swap Asgari for White as Iranian officials have suggested.