America’s secretary of state, John Kerry, denied that a split had emerged between Western powers during nuclear talks with Iran in Geneva, Switzerland this week, insisting “there was unity there with respect to getting it right.”

In an interview with NBC’s Meet the Press that was broadcast on Sunday, President Barack Obama’s top diplomat claimed that all five permanent members of the United Nations Security Council plus Germany, the six parties negotiating with Iran, “wanted to make sure that we had tough language necessary, the clarity in the language necessary, to be absolutely certain that we were doing the job and not granting more or doing something sloppily.”

Kerry unexpected joined the talks in Geneva on Friday, a day before they broke up — reportedly because the French demanded stronger concessions from the Iranians.

According to the news agency Reuters, which quoted one diplomat involved in the process as accusing France’s foreign minister Laurent Fabius of trying to “insert himself into relevance late in the negotiations,” the main sticking points included a shutdown of all Iranian reactors that can be used to produce fuel for weapons, the fate of its stockpile of higher enriched uranium and the sequencing of sanctions relief.

Economic sanctions enacted against Iran are seen as the main reason the country is willing to negotiate. Kerry argued that the situation had “changed since the election” in June that was won by the relatively moderate cleric Hassan Rouhani who had promised to alleviate his country’s suffering. “This is a new overture,” Kerry added.

Others, including Israel, which has repeatedly warned that it might attack Iran unilaterally to disable its nuclear program, are more skeptical. Laurent told French radio that he could not accept a “fool’s game,” referring to Iran offering concessions in the past only to buy itself more time.

Israel’s prime minister Benjamin Netanyahu has expressed similar worries and cautioned against lifting sanctions until Iran agrees to dismantle all facilities that could be used to produce nuclear weapons.

Kerry said there would be no such partial deal, only a first deal that “locks in” the Iranian program while comprehensive negotiations continue. But he also suggested that the United States should act in “good faith” after arguing that the sanctions had been enacted not so much to dissuade Iran from developing a nuclear weapons capacity, rather to force it into negotiations.