Mousavi made the remarks on Wednesday after Iranian Foreign Minister Mohammad Javad Zarif said in New York that Iran was ready for prisoner swap with the US.
The spokesman said that Zarif’s proposal is serious and nothing new.
Addressing an event at the Asia Society in New York on Wednesday, Zarif told Reuters he was proposing "a serious dialogue" with the United States on a possible prisoner swap.
Zarif was in New York on Wednesday to attend a UN conference dubbed 'the International Day of Multilateralism and Diplomacy for Peace.'
Soon after the Zarif’s remarks, the US State Department said in a statement that it advocated for a humanitarian resolution to the case of US citizens detained in Iran. However, it urged Iran to immediately release the American prisoners first.
“We are aware of Foreign Minister Zarif’s recent comments to a NGO in New York regarding wrongfully detained Americans in Iran. We note his reference to a humanitarian resolution of those cases, which we have called for repeatedly,” a US State Department spokesperson told US-based Al-Monitor website.
Later in the day, the Iranian foreign ministry spokesman criticized the US State Department’s "hasty" reaction to FM Zarif’s proposal, and its call for the "unilateral release" of all US prisoners.
“The reaction shows they lack a proper understanding of the concepts of negotiation, agreement, and exchange,” the Iranian spokesman noted.
Mousavi said if there is a will in the US, Zarif’s proposal is "clear" and does not require any "interpretation and clarification".
Zarif’s proposal to exchange prisoners with the United States is serious, but it’s nothing new, the Iranian spokesman said.
“The Iranian Foreign Ministry, within the framework of its responsibilities, is ready to take action on the exchange of individuals convicted and imprisoned in Iran by the country’s Judiciary on specific charges,” he said.
The Foreign Ministry would do so in exchange for both the release of all Iranians jailed in the United States and the granting of nolle prosequis to all those detained in different countries on baseless charges of violating the US’ illegal sanctions or under Washington’s pressure, Mousavi added.