John Kerry, William Hague and foreign ministers from France and Germany all made unplanned flights to Geneva on Friday in an attempt to seal a nuclear deal with Iran and end a decade-long impasse with the country.

There were also reports on Friday night that the Russian foreign minister, Sergey Lavrov, was flying in, despite earlier official denials that he would attend. The convergence on Switzerland of ministers from major world powers was meant to boost negotiations that have been under way since Thursday among senior officials.

As the talks closed on Friday night, officials were saying that the negotiations had been productive and that they would resume again on Saturday morning.

Kerry put off a planned trip to Morocco and Algeria to focus on the Geneva talks, while Iranian journalists were told to delay flights back to Tehran.

The focus of the talks shifted from formal sessions at Geneva's Palace of Nations to impromptu meetings at the European mission hosted by the EU foreign policy chief, Catherine Ashton. Kerry, Hague, the French foreign minister, Laurent Fabius, and his German counterpart, Guido Westerwelle, gathered there. After night fell, Ashton and Kerry met the Iranian foreign minister, Mohammad Javad Zarif, for three-way discussions that western officials described as the key session of the talks so far.

The officials said Kerry's arrival did not signal that a deal was ready to be signed but rather that the issues dividing the sides had risen to a level that only foreign ministers, in consultation with their heads of government, could resolve.

The aim of the talks is to agree a joint statement laying out a roadmap towards a peaceful resolution of the nuclear standoff. Iranian officials said a draft of the statement had been completed by the time Ashton, Kerry and Zarif met at the EU mission.

According to Zarif and western officials, it was to include details of an interim deal that would slow down Iranian uranium enrichment and relax some sanctions, providing time to work out a more comprehensive, long-term agreement. The outline of that goal would also be sketched out in the joint statement, on Iranian insistence. Zarif has said he does not want to negotiate piecemeal accords without knowing what the end point of the process would be.

Kerry arrived in Geneva in the early afternoon after a stormy meeting with the Israeli prime minister, Binyamin Netanyahu, who made clear that he rejected the intended interim deal with Iran on the grounds that it represented a step towards dismantling sanctions without a total halt to Iranian enrichment.

Western officials said Netanyahu's remarks were aimed at his own rightwing supporters and that his vocal opposition would eventually make it easier to "sell a deal" to the Tehran leadership and Iranian public.

The White House said President Obama called Netanyahu on Friday to smooth things over. "The president provided the prime minister with an update on negotiations in Geneva and underscored his strong commitment to preventing Iran from obtaining a nuclear weapon, which is the aim of the ongoing negotiations between the P5+1 and Iran," according to a White House description of the call. "The president and prime minister agreed to continue to stay in touch on this issue."

On arriving in Geneva, Kerry said he had come at Ashton's invitation to help close the deal with Iran.

"I want to emphasise there are still some very important issues on the table that are unresolved. It is important for those to be properly, thoroughly addressed," the US secretary of state said. "We hope to try to narrow those differences, but I don't think anybody should mistake that there are some important gaps that have to be closed."

Fabius, who arrived two hours earlier, said he had made the impromptu trip "because these negotiations are difficult but important for the regional and international security".

He said: "It is a question of reaching an agreement which represents a first solid step in addressing the international concerns over the Iranian nuclear programme. There has been a lot of progress, but so far nothing has been finalised."

Majid Takht-Ravanchi, an Iranian deputy foreign minister, confirmed in the afternoon that a draft agreement had been drawn up and would be discussed at the crucial meeting involving Ashton, Kerry and Zarif.

"The text is ready and the initial negotiations about this text will be made in this trilateral meeting," Takht-Ravanchi was quoted as saying by the semi-official Mehr news agency.

He added: "We have announced that banking and oil sanctions should also be discussed in the first step."

If that is true, and Iran is insisting on such large-scale sanction relief as part of the first step, it would signal a serious obstacle to agreement. Senior US officials have made it clear they do not think major oil and banking sanctions should be part of an initial confidence-building accord.

Meanwhile, the International Atomic Energy Agency (IAEA) confirmed that its head, Yukiya Amano, would visit Tehran on Monday in an attempt to accelerate parallel long-running talks between Iran and the agency aimed at clearing up allegations about past Iranian nuclear work.

Iran has claimed the allegations are based on forged evidence, but western intelligence claims that until at least 2003 Iran had a large-scale programme to create weapons. The IAEA has frequently complained that the previous Iranian government did not co-operate with its investigation, but agency officials have said since the election of reformist president Hassan Rouhani in June that the situation has improved.