The US State Department informed Congress on Monday that it would be waiving sanctions and unfreezing $6 billion in Iranian assets at banking institutions to be used for “humanitarian aid” in exchange for five US citizens held as prisoners in Iran. The exchange has allegedly been in the works for some time, with talks beginning as early as 2017.

Neither Congress nor the State Department have released the text of the sanctions waiver signed by Secretary of State Antony Blinken on September 8. However, several news sources obtained copies of the notification sent to Congress, prompting the State Department to outline the details of the deal Tuesday. State Department spokesperson Matthew Miller confirmed that the September 8 waiver was to release funds from a South Korean banking institution. The money then moved through Europe and eventually to Qatar. Miller then stated, “[T]hey will be available for use for humanitarian transactions with strict Treasury Department oversight, and ultimately they’re to, as we said before, effectuate the release and bring home five American citizens who have been wrongfully imprisoned in Iran.”

Miller also alleged that the money in question was originally held in these accounts so countries could purchase Iranian oil as approved by former US President Donald Trump’s administration, stating:

That there were $6 billion that were held in these funds; the previous administration set up these accounts or allowed these accounts to be set up so countries could purchase Iranian oil…And in other places, we saw them spend down the funds in these accounts, funds that – accounts that were set up for purchases of oil, for example, from – in India or Brazil, and under the previous administration were spent down with no restrictions at all. When this administration took office, we put restrictions on these accounts to ensure that they could only be used for humanitarian purposes.

Senator Chuck Grassley (R-IA) criticized the waiver, stating:

It’s ridiculous for US to be blackmailed into paying $6B for hostages which will help indirectly finance the number 1 foreign policy of Iran: terrorism Last time it was $1.7B traded for hostages next time it will probably be $10B the price keeps going up & up.

NBC News interviewed Iranian President Ebrahim Raisi about the released funds and he stated:

This money belongs to the Iranian people, the Iranian government, so the Islamic Republic of Iran will decide what to do with this money..Humanitarian means whatever the Iranian people needs, so this money will be budgeted for those needs, and the needs of the Iranian people will be decided and determined by the Iranian government.

News of the proposed prisoner exchange broke in August, when several news outlets reported that the prisoners had been moved from Evin prison to house arrest in a Tehran hotel. Three prisoners involved in the exchange have been named thus far, including Siamak Namazi, Emad Sharghi and Morad Tahbaz. Namazi in particular has been in custody for the longest, having been detained since 2015 on espionage charges.

It is unclear when the prisoners are expected to be released, but CNN has reported that inside sources claim it could be as early as next week.