FILE - Foreign Ministry spokesperson Nasser Kanaani speaks in Tehran, Iran. AP
Under the deal, which Washington and Tehran have previously confirmed, Iran would release five US citizens from detention and, Iran says, the United States would release five Iranians.
The United States and Iran also agreed to the release of the $6 billion long frozen by South Korea due to US sanctions, to be transferred to an account in Qatar for humanitarian purchases.
"We hope to have total access to the Iranian assets today," Iran's foreign ministry spokesman Nasser Kanani told a Tehran press conference.
"The prisoner exchange will take place on the same day and five Iranian citizens imprisoned in America will be released."
The exchange was brokered through Gulf states because Iran and the United States do not maintain diplomatic relations.
Iran had generated $6 billion through oil sales to South Korea, which froze the funds after the United States under former president Donald Trump reimposed sanctions as he withdrew from a landmark nuclear accord.
The five Americans -- all considered Iranian nationals by Tehran, which rejects dual nationality -- were released to house arrest when the deal was agreed last month.
Among the Americans is Siamak Namazi, a businessman arrested in 2015 on spying charges which his family has rejected.
The others are wildlife conservationist Morad Tahbaz, venture capitalist Emad Sharqi, and two others who wished to remain anonymous.
Last week, the official IRNA news agency identified the five Iranian prisoners.
They include Reza Sarhangpour and Kambiz Attar Kashani, both accused of having violated US sanctions against Tehran.
A third prisoner, Kaveh Lotfolah Afrasiabi, was detained at his home near Boston in 2021 and charged with being an Iranian government agent, according to US officials.
Two others, Mehrdad Moein Ansari and Amin Hasanzadeh, included in the deal were said to have links to Iranian security forces.
Out of the five Iranians to be released, two will return to Iran while two others will remain in the United States, upon their request, said Kanani.
A fifth Iranian prisoner will travel to a third country, he added.
The White House has denied that the unfreezing of the Iranian funds was effectively a ransom payment.
President Joe Biden's administration has insisted that Iran will only be allowed to use the money to buy food, medicine and other humanitarian goods.
Iran, which has been deeply hostile to the US since the country's 1979 Islamic Revolution overthrew its pro-Western monarch, has denied restrictions have been placed on the spending of funds.
Iran's Kanani has insisted that the money will allow Tehran to "purchase all non-sanctioned goods", not just food and medicine.
Biden took office with hopes of restoring the landmark 2015 nuclear agreement, under which Iran promised to constrain its contested nuclear work in return for sanctions relief.
But months of talks failed to produce a breakthrough.
Prospects for resolving the dispute sank further after protests broke out in Iran a year ago following the death in custody of Mahsa Amini, who had been arrested for allegedly violating the country's Islamic dress code.
The release of the funds and the prisoners would come just days after the first anniversary of her death, and just as Biden and Iran's president, Ebrahim Raisi, are in New York for the annual UN General Assembly, although they are not expected to meet.