US must guarantee it will not leave nuclear deal again, says Iran

Tehran's insistence signals that issue is still a serious obstacle after three months of talks in Vienna

A US guarantee that it will never unilaterally leave the Iran nuclear deal again is vital to a successful conclusion of talks in Vienna on the terms of Washington's return to the agreement, the Iranian ambassador to the UN, Majid Takht-Ravanchi, has said.

His comments are the clearest official signal yet that disagreements between the US and Iran on how such a guarantee might be constructed remain a serious obstacle. Donald Trump took the US out of the nuclear deal in 2018, only three years afterhis predecessor, Barack Obama, had signed it.