“These negotiations have made very good progress and continue to make progress,” Hague told reporters in Geneva, Switzerland, on Saturday.
He said that there are “still important issues” to be resolved, but that “momentum has built up” for an agreement.
“There is now a real concentration on these negotiations, so we have to do everything we can to seize the moment and seize the opportunity to reach a deal that has eluded the world,” Hague pointed out.
“It is too early to say that we will reach a successful conclusion today (Saturday),” the British foreign secretary said.
“Any agreement is going to require some flexibility on all sides... [the deal] has to be one that the world has confidence in, that the world as a whole can have confidence in,” he added.
The negotiations between Iran and the five permanent members of the UN Security Council - the United States, China, Russia, France and Britain - plus Germany over the Islamic Republic’s civilian nuclear work began in Geneva, Switzerland, on Thursday. The US secretary of state and the foreign ministers of Britain, France and Germany joined the talks on Friday.
Iranian Foreign Minister Mohammad Javad Zarif, his US counterpart John Kerry and EU High Representative for Foreign Affairs and Security Policy Catherine Ashton held trilateral talks also on Friday in the Swiss city.