John Kerry insists progress has been made despite failure to reach Iran nuclear deal "One year ago, Iran's nuclear programme was rushing at full speed," he said. Today, Iran has halted progress on its nuclear programme and it has rolled it back for the first time in a decade. As for the six days of talks in Vienna and his meetings with Mr Zarif, the secretary of state said: "In these last days in Vienna, we have made real and substantial progress and we have seen new ideas surface." Mr Kerry argued that it was worth extending the talks for seven months with the "specific goal" of reaching a "political agreement" on Iran's nuclear programme "within four months," allowing a further three for technical negotiations. "Today we are closer to a deal that would make the entire world - especially our allies and partners in Israel and the Gulf - safer and more secure," added Mr Kerry. He promised not to "sit at the negotiating table forever, absent measurable progress" and conceded that it was "absolutely" possible that a final deal would prove unattainable. But Mr Kerry said: "Given how far we have come over the past year and particularly in the last few days, this is certainly not the time to get up and walk away." However, Republicans in Congress may not be convinced. "The definition of insanity is doing the same thing over again and expecting a different result," said a senior Republican foreign policy adviser. Hopefully President Obama will finally support the vast majority of the American people who want Iran to choose between economic collapse and the dismantlement of its nuclear programme. Doing more of the same for the next seven months would be pure insanity. Mr Kerry declined to go into detail on the progress that was made in Vienna or on the stumbling blocks that prevented an agreement. But America and Iran are believed to remain at loggerheads over the scale of the latter's capacity to enrich uranium and the pace at which sanctions would be lifted under any agreement. Mr Kerry made clear that if Iran resolved all concerns about its nuclear programme and signed a final deal, then sanctions would go. "We want to terminate the sanctions - yes, we want to terminate the sanctions - which were put in place to get us to these negotiations and ultimately to be able to bring about a deal," he said. The secretary of state appealed to Congress to refrain from threatening any new sanctions on Iran and "see the wisdom of leaving us the equilibrium for a few months to be able to proceed without sending messages that might be misinterpreted." But Republicans have already promised to introduce legislation that would automatically impose sanctions if Iran were to walk away from the negotiating table. They claim to be close to securing the 67 votes in the Senate that would override the president's veto. Even if that number was not achieved, Mr Obama could be forced to veto any sanctions legislation, thereby placing him publicly at odds with Congress over a matter of national security. Hassan Rouhani, the Iranian president, echoed Mr Kerry's upbeat assessment of the failure to reach agreement in Vienna. "Our nuclear negotiation team has worked tirelessly around the clock and positive steps have indeed been taken," said Mr Rouhani. We have not yet reached a final agreement but these are steps forward.