US Secretary of State John Kerry will travel to Geneva to join international talks on Iran's disputed nuclear programme, fuelling hopes a historic deal may be in sight.
Tehran and world powers ended a first day of talks on Thursday with Iranian Foreign Minister Mohammad Javad Zarif saying a deal could be reached "before we close these negotiations”.
Negotiators from Iran and six global powers are meeting for two days in Geneva to broker a deal that could see Tehran freeze its nuclear efforts in exchange for some relief from the sanctions that have battered its economy.
There is a window of opportunity now that has been created by the Iranian people... and that opportunity needs to be seized.
Western powers suspect Iran's uranium enrichment may be aimed at developing nuclear weapons, a claim Tehran denies.
Kerry will go to the Swiss city "in an effort to help narrow differences in negotiations" and at the invitation of EU foreign policy chief Catherine Ashton, a senior State Department official said.
Upending an 11-day tour mostly of the Middle East, Kerry was due to arrive in Geneva later on Friday for the talks which had dragged for years until new Iranian President Hassan Rouhani came to power in August.
Kerry, who was in Amman on Thursday, will first fly to Tel Aviv to meet Israeli Prime Minister Benjamin Netanyahu, and his surprise decision to go to Geneva is expected to infuriate key US ally, Israel.
Speaking as he headed into a meeting with Kerry, Netanyahu said that Iran had got "the deal of the century."
"Israel utterly rejects it [Iran deal] and what I am saying is shared by many in the region, whether or not they express that publicly. Israel is not obliged by this agreement and Israel will do everything it needs to do to defend itself and the security of its people," he said.
Iranian leaders in the past have denied the Holocaust and threatened to destroy Israel.
Iran's Zarif was due to meet early on Friday with EU diplomatic chief Ashton, who is chairing the talks on behalf of the P5+1 group of world powers - permanent UN Security Council members Britain, China, France, Russia and the United States, plus Germany.
In their second meeting in Geneva in less than a month, Iranian negotiators sat down for a series of talks that Western officials described as "substantive" and "productive".
"There is a window of opportunity now that has been created by the Iranian people... and that opportunity needs to be seized," Zarif said.
In another possible indication the talks were making headway, Zarif cancelled a planned trip to Rome to stay on in Geneva.
The meeting is the second since Rouhani took office in August pledging to resolve the nuclear dispute and lift sanctions by engaging with world powers.
The US and its allies say they are encouraged by Tehran's shift to softer rhetoric since the election of Rouhani. But Western allies say Iran must back its words with action and take concrete steps to scale back its atomic work.
French Foreign Minister Laurent Fabius will also attend the international talks, his ministry announced on Friday, further fueling speculation that a historic agreement may be in sight.
The six global powers are unlikely to agree on anything less than a suspension of enrichment of uranium to 20 percent fissile purity, a level that constitutes a technical milestone not far from the threshold for a nuclear warhead.