The western parties to the talks with Iran, specially the US, have in the last few days raised excessive demands beyond earlier agreements, making the road to a draft final nuclear deal even more bumpy.
"We are very close, but if the important, historical decisions are not made in the next hours we won't have an agreement", EU foreign policy chief Federica Mogherini told CNN on Friday.
US Secretary of State John Kerry said America and other major powers were not in a rush. "We're here because we believe we are making real progress," Mr Kerry told reporters. But he cautioned that "we are not going to sit at the negotiating table forever" and that he was prepared to "call an end" to nuclear talks with Iran if "tough decisions" are not made."