Iran released five imprisoned Iranian-Americans to house arrest Thursday in the first move of a tentative agreement with the US that would unfreeze approximately $6 billion in Tehran assets held in South Korea.

While National Security Council spokeswoman Adrienne Watson hailed an “encouraging step” and warned negotiations “remain ongoing and are delicate,” Iran’s mission at the United Nations said Washington and Tehran had agreed to “reciprocally release and pardon five prisoners.”

The New York Times, citing anonymous sources, also reported the US would release “a handful” of Iranians serving time in American prisons for violating sanctions on the Islamic Republic.

The newspaper also reported the US would move the newly unfrozen funds to a bank account controlled by Qatar, a move meant to ensure Iran only uses the money for humanitarian purchases, such as food and medicine.

“We have received confirmation that Iran has released from prison five Americans who were unjustly detained and has placed them on house arrest,” Watson said in a statement. “We will continue to monitor their condition as closely as possible.”

“Of course, we will not rest until they are all back home in the United States,” she added.

In a separate statement, US-based attorney Jared Genser identified the “American hostages” as Siamak Namazi, businessman Emad Shargi, and environmentalist Morad Tahbaz, along with two other unnamed individuals.

“The move by Iran of the American hostages from Evin Prison to an expected house arrest is an important development,” said Genser, who had served as Namazi’s pro bono counsel. “While I hope this will be the first step to their ultimate release, this is at best the beginning of the end and nothing more.”

“But there are simply no guarantees about what happens from here,” he added.

Namazi, the former head of strategic planning at Dubai-based Crescent Petroleum, was arrested in 2015 and convicted on charges of cooperating with a hostile government – the United States. He was sentenced to 10 years in prison.

Namazi’s family received “direct visual confirmation” Thursday morning that the three named detainees had “been taken from Evin Prison on their way to house arrest,” Genser said just before the White House confirmation.

“While the fourth American was not directly seen leaving, given their joint presence in the prison office, it is believed that this fourth American has been moved with the other three. It appears a fifth American, an unnamed woman whose detention was only recently made public, is already under house arrest.”

The White House had notified the families of the four prisoners on Wednesday that the move was expected, the attorney went on.

“It is anticipated that the four prisoners will be held at a hotel under guard by Iranian officials under house arrest,” Genser said. “Their conditions are expected to be no worse than what they had while detained at Evin Prison.”

“This should mean, for example, that they will be able to spend time with each other and also make calls to family,” he added.

Namazi’s brother, Babak Namazi, called the move a “positive change” in a statement, but added his family “will not rest until Siamak and others are back home.”

“We continue to count the days until this can happen,” he said. “We have suffered tremendously and indescribably for eight horrific years and wish only to be reunited again as a family.”

In January, Namazi penned an open letter to President Biden demanding the commander-in-chief do more to secure his release.

“All I want sir, is one minute of your days’ time for the next seven days devoted to thinking about the tribulations of the U.S. hostages in Iran,” he wrote. “Just a single minute of your time for each year of my life that I lost in Evin prison after the U.S. Government could have saved me but didn’t. That is all. Alas, given I am in this cage all I have to offer you in return is my additional suffering.”

Republicans in Congress were dismayed at the US making concessions to return the detainees. While Sen. Lindsey Graham (R-SC) acknowledge he was “glad” to see them out of prison, he said he feared “the policy of paying a terrorist regime to release innocent Americans will just give us more terrorism.”

“The best way to protect Americans is to have countries like Iran be afraid of taking Americans hostage in the first place,” Graham wrote on X, formerly known as Twitter. “Instead of rewarding Iran for taking Americans hostage — they should fear the repercussions.”

“The current policy sends a terrible signal.”

“As long as ransom payments continue to be the US foreign policy response, #Iran will continue to take Americans and hold them hostage,” added Rep. French Hill (R-Ark.). “We must severely punish those countries that take Americans solely for their blue passport, rather than reward them with a windfall of billions.”

“While we always welcome the release of American hostages—if they are in fact released after President Biden pays Iran $6 billion in ransom—this craven act of appeasement will only embolden the ayatollahs to take more hostages,” warned Sen. Tom Cotton (R-Ark.). “Iran will also use these ill-gotten gains to attack our troops, fund terrorism, and arm Russia. This cycle will continue until President Biden stops dancing to Iran’s tune and starts responding firmly and decisively to their aggression.”

Former national security adviser John Bolton also slammed the arrangement, saying Biden was showing that “in this administration, the bazaar is open.”

“In Iran right now are 10,000 American citizens, probably of Iranian heritage, maybe with dual citizenship,” Bolton told WABC Radio’s “Cats and Cosby Show.” “10,000 Americans at risk in Iran … I think we are totally out of our minds … It’s part of this administration … trying to keep hope alive that they can go back into the 2015 nuclear deal.”

“To the rest of the world – to the Russians, to the Chinese, to every terrorist group out there … the price on an American’s head right now is $1.2 billion and may be climbing,” Bolton told host John Catsimatidis, adding that the deal “legitimizes [Iran’s] argument that these people are spies or have done something illegal.”

“These regimes are entirely cynical,” he went on. “They know exactly what they’re doing. They are building up assets to trade with us.”