Iran and the US had earlier agreed on a memorandum setting out a pathway towards a permanent settlement. The understanding included demands for the lifting of US oil sanctions, removal of the US naval blockade on Iranian ports, the unfreezing of Iranian assets abroad and an end to fighting on all fronts, including Lebanon. The agreement later unravelled, with both sides accusing each other of violating its terms.

Mohebi said Iran was now seeking the release of the entire $24 billion in frozen Iranian assets upfront, rather than receiving the funds in stages before and during negotiations.

"The issue of Yemen was not on the agenda of the previous agreement. We are now demanding that the lifting of the blockade on Yemen be included in the agreement," he said.