In the last round of nuclear talks in Vienna, Iran tightened its position, moving away from the previously proposed compromises and making additional demands, a senior US State Department official said,
He added that Iran's demands went beyond negotiations to restructure the nuclear deal.
This week, the Austrian capital hosted the seventh round of talks with Iran after a long hiatus. The State Department official said he did not know when the parties would meet again but made it clear that the seriousness of Iran's approach towards the United States was more important than the date of the new meeting.