A potential prisoner swap deal between the United States and Iran - which "remains on track," White House national security adviser Jake Sullivan told reporters this week - has renewed attention on the plight of other prisoners in Iran with Western passports who advocates say are detained as bargaining chips.

As an initial step in the emerging deal, a rare bright spot in U.S.-Iran relations, four Americans were moved from the harsh conditions of Iran's Evin Prison to house arrest. The final exchange, which remains in process, is set to include the release of five Iranian prisoners in the United States and the freeing of $6 billion in oil revenue held in South Korea under U.S. sanctions, to be used for humanitarian purposes, those familiar with the talks said earlier this month.

As the deal takes shape, the families and supporters of other foreigners detained in Iran, many on charges that advocates and activists describe as spurious and ploys for diplomatic leverage, have urged that their cases remain in the public eye.

"The Islamic regime is targeting a certain group of people, individuals with foreign citizenship, in a systematic way," said Gazelle Sharmahd, whose father, Jamshid Sharmahd, an Iranian-German citizen and U.S. permanent resident who ran a radio show that aired criticism of Iran's government, is on death row in Iran, facing terrorism charges. "My father thinks only the U.S. government can get him out."

Sharmahd held a sit-in this week in front of the State Department to protest her father's apparent exclusion from the forthcoming deal. She was joined by the family of Shahab Dalili, an Iranian citizen and U.S. permanent resident, imprisoned in Iran since 2016.

"We demand that they are also treated fair, that they are also safe," Sharmahd said Wednesday at the vigil for Jamshid Sharmahd and Dalili outside the State Department.

There are around two dozen known instances of Iranian citizens who are also Western passport holders jailed in Iran, though many more remain unpublicized, according to Carole Chedid, a board member of Hostage Aid, a D.C.-based advocacy group started by former detainees.

Rights groups say Iran has a pattern of jailing Western passport holders and dual citizens for potential swaps, a practice that amounts to state-sponsored hostage-taking.

In May, Belgium freed a former Iranian diplomat jailed on terrorism charges in exchange for a Belgian aid worker arrested in Iran last year. The Washington Post's former correspondent in Iran, Jason Rezaian, was imprisoned for 544 days, until his release in 2016.

Iran's mission to the United Nations said that five Iranian citizens in U.S. custody are to be released in the forthcoming deal. Tehran has not named the individuals. There are several Iranian nationals jailed in the United States for violating U.S. sanctions.

Among the Americans expected to be released is Siamak Namazi, an Iranian American, who has been held for nearly eight years on charges of cooperation with a hostile government, the longest duration the Islamic Republic is known to have imprisoned any American.

Sharmahd said she is happy for the Namazi family - Siamak's father, Baquer, was released last October after seven years in Iranian prison - but that it felt "like a slap in the face" when she heard her father was not part of the deal.

"Our family has four generations of Americans living in California," she said. "His case is also about the safety and security of Americans around the world."

Sharmahd said Iran abducted her father in 2020 while he was visiting Dubai. He has been held in solitary confinement in Iran ever since, she said. He could be executed any day after Iran's Supreme Court upheld his sentence in late April.

The daughter said both Germany and the United States have shirked responsibility for securing his release.

"My dad's life is not a bargaining chip," she said.

Sharmahd and Dalili are classified as U.S. nationals because of their permanent residency. Gazelle Sharmahd said her father should be treated as any U.S. citizen in a hostage-taking case.

The State Department declined to comment on Sharmahd's case.

"The Department works to ensure that any U.S. citizen or legal permanent resident - regardless of whether they have been determined to be wrongfully detained - receives appropriate assistance," a State Department official said, speaking on the condition of anonymity to discuss a sensitive issue.

German Foreign Ministry spokesperson Steffen Hebestreit said at a news conference last month that Germany was "putting pressure" on Iran however possible.

"Carrying out such a death sentence would also have serious consequences for German-Iranian relations," he said.

Hebestreit said that Iran does not recognize dual-nationalities and prison authorities denied German officials access to Sharmahd.

Tehran's brutal prison system is a pillar of the regime's authoritarian rule. Just over the last year, more than 20,000 Iranians have passed through prison as part of a crackdown on anti-government protests that challenged clerical rule. Many protesters received long prison sentences on spurious charges.

Most of the foreign and dual nationals detained are from European countries, including France, Austria, the United Kingdom, Spain and the Netherlands, according to Hostage Aid's tally.

Among them is Swedish academic Ahmadreza Jalali, who was arrested in 2016 in Iran after attending a conference. Tehran accused Jalali of spying for Israel, among other charges that his family denied, and sentenced him to death. A panel of U.N. experts said he has been subject to "severe physical and psychological ill-treatment" that amounted to torture. Last spring, Iran signaled Jalali's execution was imminent but backed off after a major international campaign.

Jalali was a Swedish resident at the time of his arrest, but Sweden granted him full citizenship in 2018 as part of an effort to secure his release.

The Swedish Foreign Ministry's press office said in an email Thursday that "a handful of Swedes are being detained in Iran."

Another one of them is a Swedish national in his thirties who was arrested in April 2022, according to Sweden's Foreign Ministry. At the time, Sweden was concluding the landmark trial of Hamid Nouri, an Iranian official charged in connection with his role in the mass execution of dissidents in Iran in 1988.

Nouri was found guilty and sentenced to life in prison. He is awaiting his appeal.

Suzy Haidamous contributed to this report.