Washington won’t allow the Iranian foreign minister to visit his country’s envoy to the UN at a US hospital unless one of the American citizens detained by Iran is released first.

Foreign Minister Mohammad Javad Zarif is currently in New York for the UN General Assembly. He was denied permission to visit Iran’s representative to the United Nations, Majid Takht-Ravanchi, who is currently undergoing cancer treatment at a Manhattan hospital.

The medical facility is located just outside a small zone in which Zarif and other members of the Iranian delegation are permitted to travel. If an Iranian delegate wishes to venture outside the zone, they must notify the US State Department and seek permission, which was not granted in this case.

“Iran has wrongfully detained several US citizens for years, to the pain of their families and friends they cannot freely visit,” a State Department spokesperson explained. “We have relayed to the Iranian mission that the travel request will be granted if Iran releases a US citizen.”

It’s not uncommon for two nations as mutually hostile as the US and Iran to hold a number of each other’s citizens in custody. After all, the entire relationship between Washington and post-revolutionary Tehran in 1979 started with one big hostage crisis. It has been part of Washington’s official line to claim the moral high ground, and demand that Iran “behaves like a normal country.” The attempt to turn a hospital visit into a prisoner exchange has therefore raised a few eyebrows.

Incidentally, this week an Iranian was extradited from the US after pleading guilty to procuring electronic equipment for Iran’s state broadcaster in violation of US sanctions. Negar Ghodskani, 40, was arrested in Australia in 2017 on a US warrant and has since remained in jail. While fighting extradition to the US, she gave birth to a child.

After being transported to the US, she pleaded guilty as part of a court bargain and was sentenced on Tuesday to 27 months, which she had already served. While Ghodskani was in custody, Tehran suggested that she could be swapped for Nazanin Zaghari-Ratcliffe, a British-Iranian woman who was arrested in Iran in 2016 for running a BBC Persian online journalism course, which Tehran considered to be teaching people to spread propaganda aimed at toppling the Iranian government.