The diplomatic progress that brought six foreign ministers tantalisingly close to a historic agreement on the Iranian nuclear programme is in danger of unravelling before negotiators meet again this month, officials and analysts warned on Sunday.

In a bid to contain the danger, the lead US negotiator, Wendy Sherman, flew straight from the talks in Geneva to Israel to reassure Binyamin Netanyahu's government that the intended deal would not harm his country's national interests.

The hastily arranged trip represented an acknowledgement of Netanyahu's power to block a deal through his influence in the US Congress and in Europe. Egged on by the Israelis, the US Senate is poised to pass new sanctions that threaten to derail the talks before they get to their planned next round in 10 days' time.

The US secretary of state, John Kerry, said on Sunday that America was sufficiently sceptical of Iran's willingness to dismantle its nuclear programme and would keep sanctions in place as talks continue.

"We are not blind and I don't think we're stupid. We have a pretty strong sense of how to measure whether or not we are acting in the interests of our country and of the globe," Kerry said on NBC's Meet the Press.

More immediately, Netanyahu demonstrated over the weekend that he could sway the Geneva talks from the inside through his relationship with Paris. It has emerged that after a call from Barack Obama on Friday evening asking him not to oppose the planned Geneva deal, Netanyahu did the opposite. He called British prime minister, David Cameron, Russian president Vladimir Putin, German chancellor Angela Merkel and French president François Hollande, asking them to block it.

Hollande, whose government shared some of Israel's concerns, agreed. It was French opposition that finally sank the bid to seal a temporary nuclear accord, after three days of intense bargaining, in the early hours of Sunday morning, but Netanyahu was quick to claim credit.

Netanyahu told cabinet colleagues: "I told them that according to the information Israel has, the impending deal is bad and dangerous – not just for us but for them too. I asked them what was the rush and I suggested that they wait and consider the matter seriously.

"The deal at once lifts the pressure of sanctions which have taken years to put in place, and leaves Iran with its nuclear and enrichment capabilities intact. Not one centrifuge is to be dismantled. These are historic decisions. I asked that they wait and I'm pleased they have decided [to do] so."

The French roadblock took Washington by surprise. There had been an initial day of discussions in Geneva on Thursday involving the Iranian foreign minister, Mohammad Javad Zarif, the EU foreign policy chief, Lady Ashton, and senior diplomats from the US, the UK, France, Germany, Russia and China, the six-nation group known as the P5+1 that has led the nuclear negotiations since 2006.

There had been an understanding that if the talks looked close to agreement, Kerry, who was in the Middle East last week, would come to Geneva to push them over the finishing line. But on Thursday night the Iranians forced his hand. Zarif announced that work on drafting an agreement would start the next morning and officials told the press Kerry would fly in the same day – putting the US secretary of state in a bind. If he stayed away and the talks failed, he would be blamed. He was weighing the possibility of personal intervention anyway, officials in Geneva said, but would have preferred to have chosen the timing and made the announcement himself.

Kerry had an uncomfortable meeting with Netanyahu at Ben Gurion airport on Friday morning in which the Israeli prime minister lectured him on the dangers of deal with Iran which loosened sanctions without halting the nuclear project. The atmosphere was so sour, the Americans opted out of a joint press appearance.

Kerry took off for Geneva, but before he landed the draft agreement was under public attack from another, more unexpected quarter. The French foreign minister, Laurent Fabius, told a French radio station that Paris would not accept a jeu des dupes – a fools' game, casting doubt on when a deal could be concluded.

He broke an agreement not to discuss the content of the negotiations in public, outlining what France saw as the sticking points: Iran's heavy-water reactor in Arak and its stock of medium-enriched uranium, which are alternative pathways to making a bomb. The 20% uranium could be easily turned into weapons-grade material if Tehran should decide to make a warhead, but Iran was refusing to ship it out of the country. The negotiators had been looking at compromises such as diluting it or turning it into oxide reactor fuel, which would make it more difficult to enrich further. But Paris was concerned that such options did not give the same level of assurance that the stockpile would not one day used for a bomb.

France's unease about Arak was even greater. Once operational, the heavy water reactor would produce plutonium with its spent fuel. It was due to be completed next year, and Iran refused to halt production, saying it was essential for producing isotopes used in medicine, agriculture and other scientific research.

A compromise was being hatched by US and Iranian officials that would allow the Iranians to carry on building the reactor over the six-month period of the interim agreement, but only to test it with dummy fuel rods and ordinary water.

The French and the Israelis believed that was too high-risk a solution that would allow the Iranians to get so close to completion that they would be able to insert enriched uranium into the reactor with very little notice and present the world with a fait accompli. Once that was done, bombing the reactor would not be an option because it would send a radioactive plume across the region.

Kerry had been hoping to address the French reservations within P5+1, but Fabius refused to back down during a session of the foreign ministers that went late into Saturday morning. Zarif observed wryly that the P5+1 seemed to need more time to negotiate with each other than with Iran.

Other western officials were furious with what they saw as a French breach of the P5+1's jealously guarded unity.

"This is about France's interests in the Gulf and the fact that Hollande is going to Israel later this month and he doesn't want the trip to turn into a nightmare," one official said. French officials said the text drafted principally by the US and Iran was significantly different from the one discussed by the P5+1. "There are two parallel processes going on here, a multilateral one that has been going on for seven years, and a bilateral one, and the two have not come together properly. The cogs have got jammed," said an European official in Geneva.

France has long suspected the Obama administration of being too ready to make a deal with Iran for short-term diplomatic gains, but as recently as a year ago a senior French official told the Guardian that ultimately an agreement would have to be made between Washington and Tehran. Paris, whatever its reservations, would not stand in its way.

That calculation clearly no longer applies. Following the two countries' falling-out over Syria, in which the French believed the Obama administration was dithering, France now feels strong enough to oppose Washington on America's most pressing foreign policy issue – a measure perhaps of America's waning influence in the world.