Amid hopes of an imminent breakthrough in talks over Iran's nuclear program, the British, French and German foreign ministers also arrived in Geneva, along with Kerry, after last-minute announcements.

Russian Foreign Minister Sergei Lavrov is expected to join talks in Geneva on Saturday, diplomatic sources said. There was no word whether China's foreign minister would join the talks.

The six powers make up the P5+1 group that is involved in the talks. It refers to the five permanent members of the UN Security Council - Britain, China, France, Russia and the US - plus Germany.

Negotiators indicated that some obstacles still remain in the way of any agreement offering sanctions reductions for nuclear concessions.

French Foreign Minister Laurent Fabius said major questioned still remained unresolved.

"France wants a credible agreement on the Iranian nuclear programme. For the moment, major questions have not yet been resolved, but we are working in Geneva in order, if possible, to achieve" a deal, Fabius said in a statement.

US Secretary of State John Kerry told reporters on his arrival in Geneva that "important gaps ... still remain," without giving further details.

The P5+1 group are considering gradually easing sanctions that have crippled Iran's economy if Iran curbs its nuclear program, including a cap on enrichment of uranium to a level that can be turned quickly to weapons use.

The six powers have discussed ending a freeze on up to $50 billion (37 billion euros) in overseas accounts and lifting some restrictions.

It was also announced Friday that UN nuclear agency chief Yukiya Amano will hold talks with senior Iranian officials in Tehran on Monday with the aim of "strengthening dialogue and cooperation," the agency said.

Netanyahu slams possible deal

Kerry arrived from Tel Aviv after talks with Israeli Prime Minister Benjamin Netanyahu said Friday that he "utterly rejects" the emerging nuclear deal between western powers and Iran.

Israel is strongly critical of any deal that lifts sanctions unless Iran is totally stripped of technology that can make nuclear arms.

Iran insists it is pursuing only nuclear energy, medical treatments and research.

"This is a very bad deal and Israel utterly rejects it. Israel is not obliged by this agreement and Israel will do everything it needs to do to defend itself and defend the security of its people," Netanyahu said.

After years without progress, there has been a major push to reach a deal on Iran's disputed nuclear program since the election of President Hasan Rouhani. The current Iranian president is viewed as a moderate compared to his predecessor, Mahmoud Ahmedinejad.

At the sidelines of the UN General Assembly in September, Secretary of State Kerry met with Foreign Minister Zarif, the highest level face-to-face meeting between US and Iranian officials in decades. President Obama also held a historic phone call with President Rouhani.

hc/rc (Reuters, AFP, AP)