No date has been set for the next round of negotiations between Iran and the United States, Iran's deputy foreign minister said ​on Saturday, adding that a framework of understanding must be agreed first, Reuters reported. 

The highest-level U.S.-Iran talks since the 1979 Islamic Revolution ended in Islamabad without agreement last weekend.

U.S. President Donald Trump has told Reuters there would probably be more direct talks this weekend, though some diplomats ​said that was unlikely given the logistics of convening in Islamabad, where the ​talks are expected to take place.