Talks between Iran and world powers over reviving the 2015 nuclear deal are currently in a state of deadlock, a French diplomatic source revealed on Thursday, expressing pessimism over the prospects of progress.

The talks have stalled since mid-March as negotiators seek to return to the landmark accord that limited Tehran's nuclear program in exchange for sanctions relief.

"The negotiations are at a point of deadlock," said the source, adding a deal had been ready back in March but had "slipped away" due to a dispute over the status of Iran's Islamic Revolution Guard Corps (IRGC).

"We are quite pessimistic," the source, who asked not to be named, said.

"Right now there is an interest in returning to the agreement but it will not always be that way," he pointed out.

EU diplomat Enrique Mora, who chairs the negotiations, is currently in Iran for talks with Iranian officials.

Iran: The ball is in Washington's court

It is noteworthy that the spokesperson for the Iranian Parliament's National Security and Foreign Policy Committee, Mahmoud Abbaszadeh Meshkiniو had said that his country is "in the process of resolving all contentious issues in the nuclear negotiations in a way that meets its ambitions," noting that "the Western side is not showing goodwill towards us."

"We believe that the West's reluctance in the negotiations is due to its efforts to obtain more concessions from Iran," Meshkini added, stressing that his country "will not offer more." 

He concluded, "The ball is in Washington's court, if negotiations are serious, then an agreement could be reached within hours."

Nuclear agreement ready, US has not made a decision

On his part, Iranian Foreign Ministry Spokesperson Saeed Khatibzadeh had confirmed that the agreement in the Vienna negotiations on lifting sanctions on Iran is ready and awaiting signature.

He added that the United States was unable to take the necessary political decision regarding the agreement, detailing that the Biden administration adheres to the approach taken by Trump instead of proving that its intentions are sincere.

Khatibzadeh stated that Iran is ready to return to Vienna negotiations if the US takes the necessary political decisions on the outstanding issues, adding that Iran is waiting for the 4+1 group to prove that the US is capable of abiding by its commitments after it unilaterally withdrew from the agreement under Trump.