Following the decision "by the Belgian Constitutional Court, we can now say that the way to implement the agreement has been opened, and the Islamic republic of Iran certainly welcomes this change," foreign ministry spokesman Nasser Kanani told reporters in Tehran.
The move would see Belgian aid worker Olivier Vandecasteele -- jailed in Iran for 40 years for several charges including spying -- swapped for Iranian official Assadollah Assadi who was convicted in Belgium for masterminding a plot to blow up a 2018 opposition event outside Paris.
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.
On Friday, however, the Belgian Constitutional Court cleared the way for a swap by rejecting a legal challenge to a law allowing prisoner exchanges with Iran.
Assadi, an Iranian diplomat who was stationed in Austria, was arrested in 2018 after Belgian, French and German security officers foiled a plot to set off a bomb at a rally outside Paris by an Iranian exiled opposition group.
After three years in detention, Assadi was sentenced in Belgium to 20 years in prison in May 2021.
"We have stated that he (Assadi) must be released unconditionally, compensation must be paid, and a commitment should be given not to repeat such actions," Kanani said, adding that "with the recent change, we hope to see an opening regarding the diplomat's case."
Vandecasteele, 42, was handed multiple sentences totalling 40 years on a range of charges on January 10, but with the sentences to run concurrently he would need to only serve 12.5 years behind bars, Iran's judiciary said noting that his verdict could be appealed.
Iran arrested Vandecasteele in February 2022, and he has since been held in conditions that Belgium's government has described as "inhumane".
Belgium insists Vandecasteele is innocent and is being held as a hostage as Tehran attempts to force Brussels to release Assadi.