The Islamic Republic says it is ready for a prisoner swap with Belgium after the constitutional court in the European country upheld an exchange treaty.

The Constitutional Court of Belgium on Friday rejected a request to annul a prisoner exchange treaty with the Islamic Republic signed last year that can lead to the release of an Iranian diplomat, Assadollah Assadi, convicted of terrorism, for Belgian aid worker Olivier Vandecasteele, held hostage in Iran.

Iran’s foreign ministry spokesperson said Monday that the ground is ready to execute the prisoner exchange pact.

"With the recent development, we hope to see an opening in connection with the case of this diplomat," added Nasser Kanaani.

However, the Belgian Supreme Court said in its ruling that plaintiffs can appeal to lower courts to block Assadi’s repatriation to Iran.

Belgian aid worker Olivier Vandecasteele was arrested on a visit to Iran in February 2022 and sentenced in January to 40 years in prison and 74 lashes on charges including spying.

Brussels gave a 20-year jail term to Assadi in 2021 over a foiled bomb plot in the first trial of an Iranian official for suspected terrorism in Europe since Iran's 1979 revolution.

Under a treaty Belgium and Iran signed in 2022, Vandecasteele would have been eligible to be swapped for Assadi but in December Belgium’s constitutional court suspended the implementation of the treaty until it could make a ruling.

Some Belgian lawmakers voiced concern that the prisoner exchange treaty might lead to "hostage diplomacy" and put other Belgians at risk of detention.