Families of Americans and a British citizen held in Iran appealed for international action Tuesday to win the release of their loved ones, accusing the regime in Tehran of engaging in "hostage taking."

A few blocks from where world leaders — including Iran's president — gathered at the U.N. General Assembly this week, relatives of prisoners in Tehran spoke to reporters to try to draw more attention to the plight of those held behind bars in Iran and to urge governments to show more urgency in winning their release.

Babak Namazi, whose Iranian American brother Siamak has been imprisoned since 2015 and whose 84-year-old father Baquer has been held since 2016, said the plight of foreign detainees was too often overlooked amid Iran's confrontation with the United States.

He and other relatives of detainees said they had given up on adopting a low profile and were now ready to speak out publicly to ensure their loved ones were not forgotten. "We can't do this alone. Please step up. Don't leave us alone in this cause that is fully and morally justified," Namazi told reporters.

"This is not an American, a British or an Iranian problem," Namazi said. "This is becoming endemic and becoming extremely important to view as an international problem."

The relatives said they had formed an organization — The Families Alliance — to raise awareness of what they called the growing phenomenon of "state hostage taking" by Iran and other governments.

Richard Ratcliffe, whose British Iranian wife Nazanin Zaghari-Ratcliffe has been imprisoned since 2016, said Western governments needed to publicly confront Iran over its detention of foreigners, which he said was clearly an effort to take hostages to gain leverage.

"The biggest criticism I have for the British government and other governments, is there's a real reluctance to name what's going on here," Ratcliffe told reporters.

Ratcliffe said he thinks Iran's approach "seems to be working. Because it's not being called out by the world, it's become the norm," he said.

Ratcliffe carried out a hunger strike in London outside the Iranian Embassy this year in solidarity with his wife, who was on hunger strike in prison. Zaghari-Ratcliffe ended her strike after 15 days.

Human rights groups have accused Iran of arbitrarily arresting foreigners — often those with dual nationality — and convicting them on baseless charges in secretive trials. The United Nations Working Group on Arbitrary Detention has declared the imprisonment of the Namazis and Zaghari-Ratcliffe illegal and demanded their unconditional release.

The Trump administration has said it is working tirelessly to secure the release of Americans imprisoned in Iran, and has called for their unconditional release.

"This administration has urgently worked to secure the release of American citizens unjustly placed in captivity and has had a great record of getting people home," said a State Department spokesperson. "We have not forgotten those who remain in captivity. Our work may not always take place in the spotlight but our efforts to get them released do not let up."

In a tweet Wednesday afternoon, a State Department spokesperson said, "President Rouhani wants the world to respect Iran. The Iranian regime must earn that respect. They can start by releasing American and other hostages."

There are about 30 known cases of foreign or dual nationals detained in Iran since 2015, and many others whose families have chosen not to make their cases public, according to a 2018 report from the U.N. special rapporteur on Iran.

President Rouhani wants the world to respect Iran. The Iranian regime must earn that respect. They can start by releasing American and other hostages. — Morgan Ortagus (@statedeptspox) September 25, 2019

"This is just the tip of the iceberg of the people that are being held there illegally, for no reason," said Ali Rezaian, whose brother Jason, a Washington Post journalist, was imprisoned for more than a year in Iran before being released.

Iran's U.N. mission in New York did not respond to a request for comment.

Iranian officials have previously rejected charges from rights groups and the U.N., saying foreigners imprisoned in the country were found guilty in legal proceedings.

Some of the relatives expressed disappointment with the approach of the United States and other Western governments, saying the detention cases appeared to be given a lower priority.

"I really think that this whole issue has been sidelined by our governments," Xua Qu said. Her husband, Princeton University scholar Xiyue Wang, has been imprisoned since 2016.

"It's all about the political will of the U.S. government," she said.

Iranian Foreign Minister Mohammad Javad Zarif has floated the possibility of swapping foreigners held in Iran for Iranian nationals imprisoned in the U.S.

Xua Qu said prisoner exchanges have been carried out in the past and she was open to any solution that would bring her husband home. But she said she was not aware of any secret talks along those lines.