Iranian Foreign Minister Mohammad Javad Zarif will fly back to Tehran and is expected to return by Tuesday to Vienna where negotiators are still at odds on some elements of a final nuclear deal, including the scope of monitoring.

Zarif¡¯s shuttle diplomacy isn¡¯t unexpected and his return to the capital for instruction could be a good thing, according to a U.S. administration official who asked not to be named in line with diplomatic rules. Negotiators will probably miss their June 30 deadline, said the source, confirming earlier reports.

¡°Tough choices will have to be made by all of us,¡± U.K. Foreign Secretary Philip Hammond told reporters on Sunday before joining the talks. ¡°There are a number of different areas where we have major differences of interpretation in the details.¡±