Iranian government officials on Wednesday called for the U.S. to release 19 Iranian nationals, who they say are in custody on charges of violating sanctions.

While Iran has in the past referred in vague terms to what it calls the issue of Iranians in American custody, the latest assertion was specific about the number being held and the reason they had been imprisoned, according to the New York Times.

“19 Iranians are in custody [in the U.S.] on charge(s) of alleged violation of U.S.-imposed sanctions,” Iranian Foreign Ministry Spokeswoman Marziyeh Afkham said Wednesday, according to the semi-official Tasnim news agency. She added that Iran urged the U.S. to end their incarceration, and lamented that international human rights bodies have kept silent on the imprisonment of these individuals.

The Iranian call represents a shift in the dialogue between the two countries over the detention of three Americans, including the Washington Post's Tehran correspondent Jason Rezaian, who has been in custody in Iran for over a year on charges of espionage and hostile acts, and faces up to 20 years in prison if convicted.

The other Americans in Iranian detention are Amir Hekmati, a former U.S. Marine serving a 10-year prison sentence for aiding a hostile country (the United States) and Saeed Abedini, a Christian pastor serving eight years on charges of undermining national security. A fourth American who was a CIA contractor remains missing after visiting the country.

The Iranian call came just one day after one of the country's senior diplomats said that Iran had no plans to swap Rezaian for Iranian prisoners held in the U.S., the first time such a high-level official had alluded the possibility of such a trade, the Associated Press report.

"An exchange of Jason Rezaian is not on the agenda. Each of the issues has their own separate case," said Hassan Qashqavi, Iran's deputy foreign minister.

Talks on the detained and missing Americans were held on the sidelines of negotiations that led to the deal involving Iran's nuclear program, seemingly without any resolution.