By Arshad Mohammed and Humeyra Pamuk
WASHINGTON (Reuters) -Five U.S. citizens detained in Iran who are expected to be swapped for five Iranians imprisoned in the United States as early as next week are "in full health," Iranian President Ebrahim Raisi said on Tuesday.
As part of the prisoner swap deal first made public on Aug. 10, the United States has agreed to the transfer of $6 billion in Iranian funds from South Korean to Qatari accounts, where they can be spent only on humanitarian goods.
The United States said it will have "oversight" on how and when the funds will be spent.
"The money can only be used for humanitarian purposes and we will remain vigilant in watching the spending of those funds and have the ability to freeze them again if we need to," State Department spokesman Matthew Miller told reporters on Tuesday.
Allowing the five Iranian Americans to leave Iran would remove a major irritant between Washington and Tehran, which remain at odds on issues from the Iranian nuclear program to Tehran's support for regional Shi'ite militias.
"They are very healthy and, according to our latest information, they are in full health," Raisi told Lester Holt of NBC Nightly News in an interview taped in Tehran on Tuesday, the U.S. television network said.
The five U.S. citizens include Siamak Namazi, 51, and Emad Sharqi, 59, as well as environmentalist Morad Tahbaz, 67, who also holds British nationality, the U.S. State Department has said, declining to identify the fourth and fifth Americans.
The five Iranians to be released by the United States are Mehrdad Moin-Ansari, Kambiz Attar-Kashani, Reza Sarhangpour-Kafrani, Amin Hassanzadeh and Kaveh Afrasiabi, according to Iran's state news agency IRNA.
IRNA, citing Iran's mission to the United Nations, said "some of the freed Iranians will remain in the United States while others will return ... home."
The prisoner exchange could take place as early as next week according to eight Iranian and other sources familiar with the deal, negotiated in indirect U.S.-Iran talks mediated by Qatar.
The United States is on track to secure the return of the five Americans in the "very near future", White House national security spokesman John Kirby told MSNBC, without giving a date.
"The arrangements have been done and the final action of swapping the prisoners should be finalized in the due time," Raisi told NBC, according to excerpts released by the network.
While Raisi appeared to acknowledge the $6 billion may only be used for humanitarian purposes, he said Iran would decide how the money would be spent.
"This money belongs to the Iranian people, the Iranian government, so the Islamic Republic of Iran will decide what to do with this money," Raisi said in the interview, speaking through an Iranian government translator.
(Reporting by Arshad Mohammed in Washington; Additional reporting by Rami Ayyub and Daphne Psaledakis in Washington and by Parisa Hafezi and Samia Nakhoul in Dubai; Editing by Timothy Gardner and Rosalba O'Brien)