Times of Israel – There are still “significant gaps” in negotiations over Iran’s nuclear program, US Secretary of State John Kerry said Saturday, warning that President Barack Obama was not prepared to extend the talks any further if real progress was not being made Kerry’s comments came in a stopover in London before he heads to Geneva Sunday for two more days of talks with Iranian Foreign Minister Mohammad Javad Zarif. World powers and Iran have set an end of March deadline for a framework agreement, with four further months for the technical work to be ironed out. The talks have missed two previous deadlines, and Obama has said a further extension would make little sense without a basis for continuing discussions. Kerry said there was no doubt Obama was serious. The president, he said, “is fully prepared to stop these talks if he feels that they’re not being met with the kind of productive decision-making necessary to prove that a program is in fact peaceful.” If the talks fail, Obama may be unable to continue holding off Congress from passing new sanctions against Iran. That, in turn, could scuttle any further diplomatic solution to US-led attempts to increase the time Tehran would need to be able to make nuclear arms. Iran denies any interest in such weapons. Skepticism about the negotiations already is strong among congressional hardliners, Washington’s closest Arab allies and Israel’s Prime Minister Benjamin Netanyahu, who is expected to strongly criticize the reported terms of the deal in an address to the US Congress early next month. Iran and the P5+1 group of Britain, China, France, Russia, the United States and Germany are trying to strike a deal that would prevent Tehran from developing a nuclear bomb in return for easing economic sanctions. Negotiators are working against the clock ahead of a March 31 deadline for agreement on the political framework of a deal. “There are still significant gaps, there is still a distance to travel,” Kerry told a press conference at the US Embassy in London. US and Iranian negotiators have been meeting in Geneva since Friday and senior P5+1 negotiators are also set to meet in the Swiss city Sunday in a bid to drive the talks forward. Kerry also used his London stop to stress the international community was “united” and “in lock step” over the negotiations. “There is absolutely no divergence whatsoever in what we believe is necessary for Iran to prove that its nuclear program is going to be peaceful,” he said earlier in the day. US Energy Secretary Ernest Moniz flew in to snow-covered Geneva on Saturday to take part in the talks for the first time, at Kerry’s request. Ali Akbar Salehi, the director of the Iranian Atomic Energy Organization, was also taking part in the negotiations. But Kerry played down any suggestion that this meant the talks were on the verge of a breakthrough. “I would not read into it any indication whatsoever,” he said, adding that Moniz was present because of the “technical” nature of the talks. The two officials were reportedly meeting Saturday afternoon. Salehi arrived Saturday morning with Zarif and Hossein Fereydoun, the brother and special aid to Iranian President Hassan Rohani, to help coordinate the talks, Iranian media reported. While the political aspects of the deal must be nailed down by the end of next month, the full agreement must be signed by June 30 — a cut-off point that looms all the larger because two previous deadlines have been missed.