Iran is ready for a full prisoner exchange with the United States, Foreign Minister Mohammad Javad Zarif said in a virtual address to the Council on Foreign Relations in New York on Monday, amid heightened tension between the longtime foes.

Washington has long demanded that Iran release U.S. citizens including Iranian-American father and son Baquer and Siamak Namazi, who it says are political prisoners.

Tehran denies it holds people for political reasons and has accused many of the foreigners in its jails of espionage. It says Iranians detained in the U.S., mostly for breaking sanctions, are being unjustly held.

“There are Iranians in U.S. prisons who are there only because they refuse to betray their country (Iran). We are prepared to exchange all of them and all those who have been kept in jail,” Zarif said.

“I repeat, we can exchange all prisoners. Period.”

The two sides have done two prisoner exchanges despite a deterioration in relations in 2018 when U.S. President Donald Trump exited Iran’s 2015 nuclear deal with major powers and re-imposed sanctions on Tehran that have crippled its economy.

Washington piled more pressure on Iran at the weekend when it said it had triggered a snapback of U.N. sanctions and slapped new sanctions on Iranian officials on Monday.

Navy veteran Michael White, detained since 2018, returned home in June in return for the United States allowing an Iranian-American physician Majid Taheri to visit Iran. White said he contracted COVID-19 while in detention.

In December 2018, Washington and Tehran worked on a prisoner exchange in which Iran freed U.S. citizen Xiyue Wang, who had been held for three years on spying charges, and the United States freed Iranian Massoud Soleimani, who faced charges of violating U.S. sanctions on Iran.