US Secretary of State Marco Rubio warned that additional pressure could be imposed on Iran if no deal is reached, with the final decision resting with US President Donald Trump.
Rubio stated that Iran's nuclear programme must remain central to any agreement, contradicting Iran's new proposal that defers discussion of the issue until the war ends.
The US has increased pressure through measures such as blocking Iranian shipping, while Tehran has tied reopening the Strait of Hormuz to progress in talks.
Rubio also raised concerns about Iran's leadership, particularly over Mojtaba Khamenei, who the US feels might not be the leader making the big calls.
