Iran said Sunday nuclear talks with world powers this week will be "difficult," as France made four demands for a deal with Tehran and Israel warned against a "nightmare" accord.
Negotiations between Iran and the so-called P5+1 -- Britain, France, the United States, Russia and China plus Germany -- restart in Geneva on Wednesday after the last round failed to seal a deal.
Top diplomats insisted they were closing in on an interim agreement that would see Iran curb or freeze parts of its nuclear programme for some relief from crippling sanctions.
Senior negotiator Abbas Araqchi said "the next round of nuclear talks will be difficult," the official IRNA news agency reported.
"No agreement will be reached without securing the rights of the Iranian nation" on its nuclear programme and uranium enrichment, he added.
Israel and the West suspect Iran is pursuing a nuclear weapons capability alongside its uranium enrichment programme, which Tehran insists is entirely peaceful.
Israel has argued that Western powers can get a better deal if they maintain or even ratchet up the sanctions, which have exacted a heavy toll on Iran's economy.
Prime Minister Benjamin Netanyahu, who welcomed French President Francois Hollande to Israel on Sunday, said he would also discuss the matter with US Secretary of State John Kerry in Jerusalem on Friday.
"I hope we'll be able to convince our friends this week and in the following days to get a much better deal. It can be achieved," he said, insisting on the need to put pressure on Iran.
"I'm concerned, gravely concerned, that this deal will go through and in one stroke of the pen, it will reduce the sanctions on Iran -- sanctions that took years to put in place -- and in return for this, Iran gives practically nothing," Netanyahu said.
"Iran's dream deal is the world's nightmare."
From Israel, Hollande laid down four demands "to guarantee any agreement" with Iran.
Signup to our newsletter and follow us on Facebook and Twitter!
Four points for deal
"The first demand: put all the Iranian nuclear installations under international supervision, right now. Second point: suspend enrichment to 20 percent. Thirdly: to reduce the existing stock.
"And finally, to halt construction of the Arak (heavy water) plant. These are the points which for us are essential to guarantee any agreement," he said.
President Hassan Rouhani has vowed to try to reassure the West over Iran's programme in order to secure the lifting of the international sanctions, but Iran insists on its right to uranium enrichment.
"Not only do we see Iran's right to uranium enrichment as non-negotiable, but we do not see any need for it to be recognised by others, since it is an integral part of Iran's rights under the Non-Proliferation Treaty," Foreign Minister Mohammad Javad Zarif told ISNA news agency.
Last week Kerry argued that Iran's right to enrich depends on it providing assurances to the international community that it is not pursuing an atomic bomb.
Zarif said no one in the P5+1 had asked Iran to stop uranium enrichment. "The full suspension of enrichment is our red line and we do not cross it," he said.
The mooted deal has come also under criticism from hardliners in Iran opposed to any concessions to the West and the US Congress threatening further sanctions.
US President Barack Obama's administration wants to offer Iran some "modest" and "reversible" sanctions relief as part of an interim deal to bolster Rouhani's negotiators and buy time for reaching a comprehensive accord.
Zarif said "all measures taken by all parties in the first phase are reversible, if no favourable result is achieved", while insisting he remained optimistic about reaching a deal.
Kerry said Iran had baulked at an offer agreed upon by the P5+1 at the latest round of talks, but Iran and Russia said French objections had scuppered a draft thrashed out by Tehran and Washington.
France has concerns about the Arak heavy water reactor, which would generate plutonium as a by-product and give Tehran a second possible route to an atomic weapon.
Hollande said at the start of his three-day visit to Israel that his country "will not tolerate nuclear proliferation".