“We said some time ago that we are ready to exchange all prisoners without preconditions… but Americans have not responded yet,” government spokesman Ali Rabiei said.

“It now appears that Americans are more ready than before to end this situation,” he added, implying that Iran was waiting for a reply.

“Washington is aware of our readiness and we think there is no need for a third country to mediate between Tehran and Washington for the prisoner exchange,” Rabiei said.

“However, if the American side agrees, the interest section of Iran in Washington will inform the US of our views on the details, including how and when the exchange will take place.”

Tehran and Washington cut diplomatic relations shortly after Iran’s 1979 Islamic Revolution. Switzerland looks after US interests with Tehran.

Rabiei also expressed concern about the health of some Iranian prisoners detained in the United States and said they are not being treated well.

“We are worried about the safety and health of jailed Iranians in America … We hold America responsible for their safety amid the coronavirus outbreak,” Rabiei said.

One of them is Sirous Asgari, an Iranian scientist infected with the novel coronavirus while in detention, according to the Iranian Foreign Ministry.

Foreign Ministry spokesman Seyyed Abbas Mousavi said Monday that “everything is prepared” and declared “he will soon return to Iran”.

Foreign Minister Mohammad Javad Zarif said in December that Tehran was ready for a full prisoner exchange with the United States, tweeting: “The ball is in the US’ court”.

Last December, Iran freed US citizen Xiyue Wang, who had been held for three years on spying charges, and the United States released Iranian Massoud Soleimani, who faced charges of violating US sanctions on Iran.

Several dozen Iranians are being held in US prisons, many of them for “breaking American sanctions” on Iran.

Iran is holding US citizens Siamak Namazi, convicted on charges that include espionage, his father Baqer, and Morad Tahbaz.

According to the US State Department, Iran temporarily released US Navy veteran Micheal White on March 19.

Both countries have called for releasing prisoners over the virus outbreak.

If a swap goes ahead, it would be one of the very few instances of cooperation in an otherwise deeply frayed US-Iran relationship, which has grown more hostile since US President Donald Trump took office.

Iran is battling what is West Asia’s most deadly outbreak, while the US has reported the highest total number of virus deaths worldwide.

The Islamic Republic has temporarily released more than 100,000 inmates in several stages since March, according to its judiciary.

Iran and the US have been at loggerheads for decades.

Tensions between them have escalated since 2018 when Trump withdrew the US from a landmark nuclear accord and reimposed sanctions on Iran.

Animosity reached historic heights in early January when top Iranian military commander Lieutenant General Qassem Soleimani was assassinated in a US drone strike in Baghdad. Iran retaliated on Jan. 9 by firing missiles at bases in Iraq where US troops were stationed.

AFP and Reuters contributed to this story.