The Biden administration is holding indirect discussions with Iran on a possible prisoner exchange to secure the release of American citizens imprisoned in Iran, with Qatar and the United Kingdom playing an intermediary role in the talks, according to NBC news channel.

It quoted four unnamed sources saying that the negotiations made progress, but it remains unclear if a final agreement would be reached.

Three sources with knowledge of the talks said the two sides were exploring a formula that has been discussed previously, dating to 2021, that could include a possible prisoner exchange and the release of billions of dollars in funds in South Korean banks currently blocked by US sanctions.

The proposed formula would allow Iran access to the funds but only for purchasing food, medicine, or other humanitarian purposes, following the existing US sanctions against Iran.

The sources noted that US and Iranian diplomats had explored possible arrangements to transfer the frozen funds, with a third country, such as Qatar, possibly overseeing the transfer.

This month, Qatari Foreign Minister Mohammed bin Abdulrahman Al-Thani met his Iranian counterpart, Hossein Amir-Abdollahian.

The Qatari delegation “conveyed messages from the US to the Iranians, including points on the prisoner release.”

In an interview this month with the National Public Radio (NPR), Amir-Abdollahian said discussions were underway on a possible prisoner swap with third parties helping to relay messages.

He said a “UK official” was acting as a “representative” for the US in the talks.

Asked about possible indirect negotiations, US State Department spokesman Ned Price said he could not confirm every detail in the report but noted that Washington has its methods to relay messages to Iran.

Price indicated that he would not be able to get into the details of what it is that may be underway, given the sensitivity of the discussions.

He said: “We’ve been unambiguous with the Iranian regime about the priority we attach to seeing the safe and prompt returns of the three Americans that are currently wrongfully held in Iran.”

“We are committed to doing everything that we can to secure the freedom of the US citizens who continue to be wrongfully detained in Iran, to bring home Siamak Namazi, Emad Shargi, and Morad Tahbaz just as soon as we can.”

Iran’s UN mission in New York did not respond to a request for comment.

Namazi has been in an Iranian prison for more than seven years, longer than any US citizen.

Iranian authorities sentenced him to ten years on charges of “collaboration with a hostile foreign government.”

Namazi accused successive US administrations of failing to secure his release and finally went on a week-long hunger strike.

The push by the White House comes after months of negotiations to revive a 2015 nuclear agreement have stalled and as the administration has announced new sanctions against Tehran over its delivery of drones to Russia.