UN Secretary General António Guterres has reportedly written a letter to the Iranian president, Hassan Rouhani, asking for the release on humanitarian grounds of Baqer Namazi, an 81-year-old retired UNICEF official, according to a report by Foreign Policy.

Baqer Namazi, an Iranian-American had apparently traveled to Iran in the hope of negotiating his son’s release. He was arrested in February 2016 in Tehran. According to the report, Guterres sent his letter to Rouhani asking for Namazi's release last week.

Baqer Namazi's 46-year-old son, Siamak, a former head of Strategic Planning Department with the Crescent Oil Company, had been arrested in Iran four months earlier. Both men were accused of espionage by the Iranian revolutionary court and sentenced to 10 years in prison. They were accused of allegedly collaborating with a foreign government, the United States.

“I am worried about my father’s heart problems and I’m afraid he’s going to die behind bars,” Baqer Namazi’s elder son, Babak, told Foreign Policy.

UN officials have emphasized that Guterres is acting out of humanitarian concern for Namazi [a former U.N. staffer] and not at the instruction of the U.S. government.

On May 7, several members of the U.S. House of Representatives called Donald Trump’s administration to secure unconditional release of all Iranian Americans incarcerated in Iran.

Furthermore, the U.S. Permanent Representative at the UN, Nikki Haley, also called for Namazi's release on June 15. “Detaining political prisoners is one of the worst human rights abuses a country can do,” Haley wrote on her twitter account in a statement after meeting Baqer Namazi. “Iran is doing just that with two of our citizens.” Haley tweeted.