FILE PHOTO: Iran's Foreign Minister Mohammad Javad Zarif attends a news conference, a day ahead of the first meeting of the new Syrian Constitutional Committee at the Untied Nations in Geneva, Switzerland, October 29, 2019. REUTERS/Denis Balibouse

DUBAI (Reuters) - Iran’s Foreign Minister Mohammad Javad Zarif said on Monday the Islamic republic is ready for a full prisoner exchange with the United States, tweeting: “The ball is in the US’ court”.

“After getting our hostage back this week, fully ready for comprehensive prisoner exchange,” Zarif said.

The United States and Iran on Saturday swapped prisoners - American graduate student Xiyue Wang, detained for three years on spying charges, and imprisoned Iranian stem-cell researcher Massoud Soleimani, accused of sanction violations - in a rare act of cooperation between two longtime foes.

Separately, Iranian government spokesman Ali Rabiei said Iran had always sought an “all for all release” with the United States.

“We are ready to cooperate to return all Iranians who are being held unjustly in America,” Rabiei was quoted by the state news agency IRNA as saying.

Rabiei said efforts to swap prisoners were not linked to any other U.S.-Iranian talks, which would only be possible if Washington lifted sanctions and returned to Tehran’s 2015 nuclear deal with world powers.

Tensions have heightened between Iran and the United States since U.S. President Donald Trump last year pulled Washington out of the nuclear deal and reimposed sanctions that have crippled Tehran’s economy. Iran has responded by gradually scaling back its commitments under the agreement.

Washington has demanded that Iran release the Americans it is holding, including father and son Siamak and Baquer Namazi; Michael R. White, a Navy veteran imprisoned last year; and Robert Levinson, a former FBI agent missing since 2007.

Several dozen Iranians are being held in U.S. prisons, many of them for breaking sanctions.