When Barry Rosen, one of those held in Tehran's American embassy in the 1979-81 crisis, saw coverage of the talks in Vienna on reviving the 2015 nuclear deal, he felt there was one glaring omission.
Rosen, 77, says he saw "nothing in the press, anywhere, about the plight of the hostages," referring to the dozen or so Westerners being held either in prison or under house arrest in Iran.
Rosen decided to come to the Austrian capital and go on hunger strike in their support, AFP said.
"It's been 40 years since I was freed and now I said to myself I have to do something about this," Rosen told AFP, sporting a black cap with the slogan "free the hostages".
"I suffered from 1979 to 1981 and I just don't want more people suffering all the time," he said in front of the five-star Palais Coburg hotel that is hosting the diplomatic talks.
It's also where Rosen has set up his base, although strict security means he can't get anywhere near the delegations.
He ended his hunger strike on Sunday after being urged to do so by his supporters due to the "deleterious effect" on his health.
His message for Tehran's interlocutors is clear: "Tell Iran to release all the prisoners immediately and if they don't do that, don't sign the nuclear accord."
- Growing movement -
Among those who have taken notice of Rosen's message is the top US negotiator for the talks Rob Malley, who met Rosen several times last week.
Rosen says Malley assured him that those currently held in Iran would not be forgotten.
On Monday Malley tweeted, "applauding (Rosen's) heroic efforts to secure the release of all wrongfully detained foreign/dual nationals in Iran".
"We remain fully focused on this crisis," Malley added.
Also on Monday Iran's foreign ministry signaled it was "possible" to reach deals on both the nuclear issue and that of detainees.
"If the other party (the US) has the determination, there is the possibility that we reach a reliable and lasting agreement in both of them in the shortest time," ministry spokesman Saeed Khatibzadeh told reporters.
On Monday the US State Department said that "it would not serve our purposes, it would not serve their interests" to link the fate of the detainees with the nuclear negotiations.
"We want the return of these Americans to be a certain proposition. And so we are keeping these issues separate," State Department spokesman Ned Price said in a statement.
Most of the Westerners detained in Iran also have Iranian nationality and stand accused of crimes such as espionage -- charges their families dismiss as ridiculous.
Some have also decided to go on hunger strike.
British-Iranian engineer Anoosheh Ashoori, 67, has stopped eating and 36-year-old French national Benjamin Briere, who insists he was in Iran as a tourist, has been refusing food since Christmas Day 2021.
Another detainee, 58-year-old Austrian-Iranian businessman Kamran Ghaderi, began his own hunger strike on Monday, his wife Harika told AFP.
She has also met Rosen and hailed what Malley said as "a good sign".
"All these countries are here, why shouldn't (prisoners) be a topic," she said of the current negotiations.
Ghaderi was arrested in January 2016 and Harika says "my eight-year-old son cannot remember his father and is asking every day when he is coming back."
- 'Keep the momentum' -
Nizar Zakka, a Lebanese-American held in Iran between 2015 and 2019, has also come to Vienna.
Now president of the Hostage Aid campaign group, said he was "excited" about the impact that the current protests are achieving.
"Now we need to keep the momentum," he says, adding that the final goal is for "all of (the detainees) to be released".
Some experts caution that linking the issue of prisoners and Iran's nuclear program may prove tricky.
The talks are aimed at reviving the moribund 2015 deal -- also known as the JCPOA -- which offered Iran sanctions relief in return for strict curbs on its nuclear program to make sure it couldn't develop a nuclear weapon.
But the deal has been disintegrating ever since former US President Donald Trump pulled out of it in 2018 and reimposed sanctions.
"It is my understanding that the US has a separate process for discussing this (hostage) issue. It should not be mixed up with the nuclear talks, which are complicated enough," says Barbara Slavin of the Atlantic Council think tank.
The talks are currently making slow progress and are facing several sticking points, notably Tehran's insistence on guarantees that a future US administration won't repeat Trump's actions.
"Iran should free the detainees, no matter what happens with the JCPOA," says Slavin.
