The Qatari plane was on standby after the US and Iran were told, according to a source briefed on the matter, that the funds had been transferred to accounts in Qatar. "US detainees are being transported to the Qatari jet," the source said.
The funds' release triggered an exchange sequence agreed after months of talks between the United States and Iran, who are at odds over Tehran's nuclear ambitions and other issues.
The five Americans with dual nationality are due to fly to Doha and then on to the US Two relatives are also expected to be on the flight. "They are in good health," an Iranian official briefed on the process said about the detainees.
In return, five Iranians detained in the US will be released. The Iranian Foreign ministry spokesperson said two Iranians would return to Iran while two would stay in the US at their request. One detainee would join his family in a third country, he added.
Iran's Foreign Ministry spokesperson Nasser Kanaani said the funds, blocked in South Korea after US sanctions on Iran were hardened in 2018, would be available to
Tehran on Monday. Under the deal, Qatar will ensure it is spent on humanitarian goods.
The deal will remove a major irritant between the US, which brands Tehran a state sponsor of terrorism, and Iran, which calls Washington the "Great Satan".
But they remain deeply divided on other issues ranging from Iran's nuclear programme and its influence around the region to US sanctions and America's military presence in the Gulf.
Qatar, a tiny but hugely wealthy Gulf Arab energy producer, has sought to raise its global profile, hosting the soccer World Cup last year and carving out a role in international diplomacy. The Sunni nation hosts a big US military base but has also forged close ties with Shia Iran.
Doha hosted at least eight rounds of talks with Iranian and US negotiators sitting in separate hotels, speaking via shuttle diplomacy, a source previously told Reuters.
Under the agreement, Doha agreed to monitor how Iran spends the unfrozen funds to ensure the cash is spent on humanitarian goods, such as food and medicine, and not any items under US sanctions.
The transfer of Iran's funds has drawn criticism from US Republicans who say President Joe Biden, a Democrat, is in effect paying a ransom for US citizens
The US dual citizens to be released include Siamak Namazi, 51, and Emad Sharqi, 59, both businessmen, and Morad Tahbaz, 67, an environmentalist who also holds British nationality. They were released from prison and put under house arrest last month.
A fourth US citizen was also released into house arrest, while a fifth was already under house arrest. Their identities have not been disclosed.
Iranian officials have named the five Iranians to be released by the US as Mehrdad Moin-Ansari, Kambiz Attar-Kashani, Reza Sarhangpour-Kafrani, Amin Hassanzadeh and Kaveh Afrasiabi. Two Iranian officials previously said that Afrasiabi would remain in the United States but had not mentioned others.
Ties between Washington and Tehran have been boiling since Donald Trump, a Republican, pulled the US out of a nuclear deal between Iran and global powers when he was president in 2018. Reaching another nuclear deal has gained little traction since, as Biden prepares for the 2024 US election.
As a first step in the deal, Washington waived sanctions to allow the transfer of $6 billion in Iranian funds from South Korea to Qatar. The funds were blocked in South Korea, normally one of Iran's largest oil customers, when Washington imposed sweeping financial sanctions on Tehran and the cash could not be transferred.
