The negotiators of the Vienna nuclear deal have made progress on how the United States will return to its obligations under the agreement, said the official representative of the Iranian Foreign Ministry Saeed Khatibzadeh.

According to Khatibzadeh, the negotiations are going on very difficult, because Iran must make sure that the United States will really fulfill all its obligations this time.

Iranian authorities will not rush to negotiate a nuclear deal and make additional concessions to revive the agreement, Iranian government spokesman Ali Rabia said.