Diplomats insisted Sunday they were closing in on an agreement to curb Iran's nuclear programme despite the failure to clinch a long-sought deal in high-profile, marathon negotiations in Geneva.
Israel meanwhile doubled down on efforts to avert a "bad deal," as Tehran insisted it would not abandon its "right" to enrichment and Secretary of State John Kerry said Washington was neither "blind" nor "stupid" about the Islamic republic's nuclear ambitions.
Hopes had soared after top world diplomats rushed to Geneva to join talks, but faded as cracks began to appear among world powers when France raised concerns over a heavy water reactor being built at Arak.
But diplomats insisted they were zeroing in on an agreement to lift some of the crippling sanctions on Iran in return for the freezing of much of its nuclear programme, and planned to meet again on November 20.
Foreign Minister Sergei Lavrov of Russia -- one of six world powers negotiating with Iran, said Tehran had been "decisive" in the "very substantial" talks aimed at renouncing "threats and sanctions".
His British counterpart William Hague -- who also attended the Geneva talks -- said it was "vital to keep the momentum" and insisted "a deal is on the table and can be done."
The pause in talks has given a window of opportunity for opponents, particularly Israel, to derail the deal, which sees Iran's nuclear programme as a threat to its existence.
Prime Minister Benjamin Netanyahu said Israel would do all it could to keep the so-called P5+1 group of world powers -- Britain, France, the United States, Russia and China plus Germany -- from striking a "bad and dangerous" deal with Iran.
The short-term deal would have reportedly frozen or curbed some of Iran's nuclear activities, which Israel and the West suspect are aimed at developing the ability to build a nuclear weapon.
Iran, which insists its programme is entirely peaceful, would receive limited relief from sanctions battering its ailing economy while the two sides worked on a comprehensive agreement.
Israel asks 'Why the rush?'
Israel -- the region's sole if undeclared nuclear-armed state -- fears an agreement would remove sanctions while allowing Tehran to enrich uranium and advance work on the plutonium reactor at Arak.
"I asked them what was the rush? I suggested they wait," Netanyahu said, recounting conversations with leaders of the United States, Russia, France, Germany and Britain.
"I hope they reach a good agreement, and we will do all we can to convince world powers to avoid a bad deal."
The hardline Iranian Kayhan newspaper warned in an editorial that "rushing into an agreement would prompt the enemies to think Iran is desperately in need of one, and therefore is ready to give major concessions."
Iran's President Hassan Rouhani sought to allay such concerns as he pleaded for the conservative-dominated parliament's support.
"There are red lines that must not be crossed," ISNA news agency quoted him as saying.
"The rights of the Iranian nation and our national interests are a red line. So are nuclear rights under the framework of international regulations, which include enrichment on Iranian soil."
Kerry offered similar assurances about the US position, saying Washington is "not blind, and I don't think we're stupid," and insisting there is "zero gap" between the White House and its commitment to Israel.
Diplomats have seen a window of opportunity for the decade-long nuclear talks following this year's election of Rouhani, a reputed moderate who has vowed to engage with the West.
Rouhani hopes to bring about the lifting of US and European sanctions that have more than halved Iran's oil exports, created serious obstacles in repatriating petrodollars and provoked rampant inflation.
One of the main stumbling blocks in the most recent talks was the Arak reactor, which is at least a year away from becoming operational but would eventually give Iran a second route to an atomic bomb by producing plutonium as a by-product.
Foreign Minister Mohammad Javad Zarif did not rule out further talks over the reactor.
"We insist on our (nuclear) rights and technology but at the same time we are prepared to remove concerns of the other parties," he said, adding Iran "does not want anyone to think we seek weapons through enrichment or the heavy water" facility.
Final say on Iran's nuclear work rests with supreme leader Ayatollah Ali Khamenei, who had expressed support for Iranian negotiators but also voiced pessimism about a breakthrough in the talks, citing decades of hostility and mistrust.