Iran's President Hassan Rouhani arrives at the Jose Marti International Airport in Havana, Cuba, on Sept. 20. (Enrique De La Osa/Reuters)

This is the third time Kamran Foroughi has flown here from London for the U.N. General Assembly, a private citizen hoping for success where diplomats have failed.

Two years ago, he delivered a letter to the Iranian mission pleading for his ailing father’s release from prison. Last year, he managed to attend a dinner for President Hassan Rouhani and handed an aide a second letter. Now, he has another letter asking Rouhani to release Kamal Foroughi, 77, on humanitarian grounds. The ­British-Iranian dual national has cataracts, spent 18 months in solitary confinement, and is more than halfway through his seven-year sentence on espionage charges.

“It feels a lot like ‘Groundhog Day’ to me,” Kamran Foroughi said.

He has company in his quest. Foroughi came to New York with Richard Ratcliffe, whose wife, Nazanin, also a British-Iranian dual national, was sentenced last month to five years in prison on espionage charges while visiting her parents. Their 2-year-old daughter, Gabriella, has had her passport confiscated.

Relatives of several of the other prisoners arrested on what their families and governments consider trumped-up charges are also making public appeals.

A growing number of dual nationals, a status Iran does not recognize, have been arrested in recent months by the hard-line Revolutionary Guard Corps in what is likely a message to the moderate Rouhani administration that negotiated the nuclear deal with six global powers, including the United States, and wants to end Iran’s international isolation.

“It’s a clear attempt to embarrass their own government,” said Ratcliffe, who keeps track of his wife’s 171 days in captivity on a calendar at home.

Nizar Zakka, a Lebanese citizen and State Department subcontractor living in the Washington area, was sentenced Monday to 10 years in prison and a $4.2 million fine, according to his supporters. His sentence has not been officially announced, but state media have called him a spy with links to U.S. intelligence services.

Jason Poblete, an Alexandria lawyer representing Zakka, urged Secretary of State John F. Kerry and U.N. Ambassador Samantha Power to ask Rouhani for Zakka’s unconditional release.

The same judge, Abolghassem Salavati, presided over the trials of Zakka, Foroughi and Ratcliffe. He is known for handing down harsh sentences in high-profile political cases. He also sentenced Washington Post reporter Jason Rezaian, who was released along with three other Iranian Americans in a prisoner swap in January when the nuclear deal was implemented.

In New York, Ratcliffe and Foroughi met privately with Rezaian and his brother Ali, who actively campaigned for his brother’s release. They discussed strategies for publicizing the fate of their loved ones.

At least three U.S. citizens with dual nationality are known to be imprisoned in Iran. Siamak Namazi, a prominent Iranian American businessman, and his father, Baquer, also a dual national, are facing espionage charges.

“Court dates have been set for Baquer and Siamak, and we hope that the judge will show the independence of the judiciary and acquit them of the baseless charges against both of them,” said Bijan Khajehpour, a former business partner of Siamak Namazi who intends to come to New York next week to meet with U.N. officials.

In addition, Robin Shahini of San Diego was detained in July.

And the United States is still looking for information about Robert Levinson, a former FBI agent who disappeared in Iran in 2007.

Several other Westerners are thought to be held in Iran, including some whose cases have not been made public.

Ratcliffe has spoken once with his wife since she was sentenced last week. She was less concerned about her own fate than about that of their daughter.

“She told me she has missed more than a fifth of Gabriella’s life while she has been in prison,” he said. “She’ll never get that time back.”