News of the agreement first broke on Thursday as US news outlets reported that four American detainees had been transferred from Tehran’s notorious Evin prison to house arrest in a hotel. A fifth prisoner had been released earlier.

Both US and Iranian officials later confirmed the first steps of the agreement but have given differing accounts of what it involves.

Barbara Slavin, a fellow at the US-based Stimson Center think tank, told Al Jazeera that the early details of the deal showed Tehran was at least partially willing to “de-escalate tensions” with Washington as it seeks a reprieve from crushing US sanctions.

She said that while the preliminary agreement “is an important step”, particularly for the families of the detainees, it is unlikely to represent a larger change in US-Iran relations.

“It doesn’t fundamentally change the nature of Iran’s relations with the United States or the international community,” Slavin said.

Here’s what we know so far about the deal:

What are the details?

Citing sources familiar with the agreement, The New York Times newspaper and several news agencies reported on Thursday that the deal, which has been months in the making, will see the eventual release of the five US prisoners.

Three of the prisoners were named as Siamak Namazi, Emad Sharghi and Morad Tahbaz. The families of the two others have withheld their identities, but they are said to be a scientist and a businessman.

Jared Genser, a lawyer for Namazi, welcomed the transfer to house arrest but said “there are simply no guarantees” about what happens next. “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,” he said.

As part of the purported deal, the US will free five Iranian prisoners in return for the release of the detained Americans, the news outlets reported.

Iran also will be given access to about $6bn in oil revenue that was frozen in South Korea due to US sanctions. Under the scheme, the money would be transferred to Qatar to oversee.

Sources told several news agencies that Iran would be able to access the funds only for humanitarian purchases, such as food and medicine, and would not directly receive any money.

US Secretary of State Antony Blinken also said on Thursday that the funds would be in “restricted accounts” that can be accessed only for “humanitarian purposes”.

The restriction is an apparent attempt by the administration of US President Joe Biden to stem criticism that the released funds could be used to boost Iran’s government and weapons programme.

However, Iranian officials have offered a different characterisation, saying Tehran will decide how to use the funds.

The logistics of setting up a mechanism with Qatar also are expected to take weeks to sort out, given the complex nature of the scheme. Qatar worked with Oman and Switzerland in mediating the negotiations.

What has Iran said?

On Friday, Iran’s Ministry of Foreign Affairs said in a statement that the “process of releasing several billion dollars of Iranian assets which had been illegally frozen by the United States in South Korea has begun”, according to the state-run IRNA news agency.

It added: “Iran will determine how to use these assets, and they will be consumed to meet different needs of the country as determined by the related authorities.”

Iran’s semi-official Tasnim news agency said the funds were first to be converted from South Korean won into euros and then sent to an account in Qatar that Iran could access.

An earlier statement from Iran’s mission to the United Nations said Tehran and Washington “agreed to reciprocally release and pardon five prisoners”.

“The transfer of these prisoners … out of prison marks a significant initial step in the implementation of this agreement,” it said.

It remains unclear which Iranian prisoners are part of the tentative deal. The New York Times reported on Thursday that “a handful of Iranian nationals serving prison sentences for violating sanctions on Iran” would be released.

What has the US said?

Blinken has called the transfer of the prisoners “the beginning of the end of their nightmare and the nightmare that their families have experienced”.

Speaking on Thursday, the top US diplomat added, however, that “there’s more work to be done to actually bring them home”.

Blinken also denied that the deal amounted to “sanctions relief” for Iran.

“We will continue to enforce all of our sanctions. We will continue to push back resolutely against Iran’s destabilising activities in the region and beyond. … None of these efforts take away from that,” he said.

Still, Republicans quickly attacked the administration of Biden, a Democrat, as news of the potential deal emerged, saying it would ease economic pressure on Iran. Senator Tom Cotton accused Biden of a “craven act of appeasement” that would “embolden” Iranian leaders.

There has been no indication that the prisoner deal would spur movement on restoring the 2015 Iran nuclear accord, which saw Tehran scale back its nuclear programme in exchange for a lifting of international sanctions against its economy.

Former US President Donald Trump withdrew from the agreement unilaterally in 2018 and instead pursued a “maximum pressure” policy against Iran, heaping sanctions on the country.

While the Biden administration initially expressed optimism about restoring the pact, it has more recently dismissed prospects of a breakthrough after efforts to revive the deal collapsed. Biden also has continued to impose new sanctions on Tehran.

Who are the US prisoners?

Namazi, a businessman in his early 50s with dual US-Iranian citizenship, was detained in 2015 while visiting his family in Tehran.

Months later, his ailing father, Baquer, was detained after returning to Iran to visit his jailed son. They were both sentenced in 2016 to 10 years in prison for spying and cooperating with the US government, charges that Washington has rejected as false.

Baquer Namazi, a former Iranian provincial governor and former UNICEF official who also has dual citizenship, was put under house arrest in 2018 on medical grounds and left Iran last year for medical treatment.

Sharghi is also an Iranian-American businessman. He was first arrested in 2018 when working for the Saravan Holding tech investment company after moving with his wife from the US to Iran.

He was released on bail after eight months and cleared of spying and security-related charges but was banned from travelling. He was summoned by a separate court in 2020 and then sentenced to 10 years for espionage.

Tahbaz, an Iranian-American environmentalist who also holds British citizenship, was arrested in 2018. He was sentenced to 10 years in prison in 2019 for “assembly and collusion against Iran’s national security” and “contacts with the US enemy government … for the purpose of spying”.