The Iranian-American wife of Shahab Dalili who has been detained in Iran for six years, has asked the Biden administration to secure the release of her husband.

Nahid Dalili told NBC News on Tuesday that she fears Washington and Tehran are close to a prisoner swap deal but her husband will be left behind.

Fifty-nine-year-old Dalili, who was arrested in 2016 while visiting Tehran for his father’s funeral charged with "aiding and abetting" the US, is a legal permanent resident, but not a citizen.

Nahid said she hadn’t spoken publicly about her husband’s case out of fear of jeopardizing his possible release, but when she heard US officials in the Biden administration refer to “four” Americans imprisoned in Iran, she decided in March to break her silence.

“I want them to hear me. They can’t say they didn’t know about this,” she said. “The Biden administration shouldn’t leave Shahab behind. He is a permanent legal resident, and all of his family are citizens.”

British Iranian Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori were freed in March after the UK paid a four-decade-old £400m ($522 million) debt to Iran.

Iran is still holding several other western dual nationals including American-Iranians Siyamak Namazi and his elderly father Bagher, American-Iranian businessman Emad Sharghi, and German-Iranian rights activist Nahid Taghavi.