Strong French declarations on Iran may win praise in Israel but are no guarantee Paris will advance a deal acceptable to the Israelis when nuclear talks resume, experts warned Monday.

On his first state visit to Israel, President Francois Hollande was warmly received after France took a tougher stance than its Western partners in the latest world powers' bid to reach a deal to scale back Tehran's nuclear programme in talks in Geneva that ended on November 10.

France "will not tolerate nuclear proliferation", Hollande pledged on arrival in Israel on Sunday, three days before the P5+1 group of world powers are to resume the negotiations with Iran.

But Israeli commentators rushed to dampen enthusiasm over its new-found ally on the Iran issue, after tensions soared between the Jewish state and Washington over the proposed interim deal.

Prime Minister Benjamin Netanyahu has repeatedly sounded the alarm over handing Iran "the deal of the century" by offering it some sanctions relief without blocking its ability to convert its nuclear programme to military ends.

"What is perceived here as a renewed honeymoon, a return to the relations that existed between France and Israel in the mid-1960s, could cause disappointment to anyone who has raised their expectations to new heights," wrote Shimon Shiffer in the top-selling Yediot Aharonot.

"Hollande may have promised that France would never permit Iran to obtain nuclear weapons, but as of now, France is falling in line on this matter with the world powers that are conducting the negotiations," he said.

And Maariv's Nadav Eyal said Israel appeared blissfully ignorant of Hollande's domestic problems and flatlining popularity back home.

"Netanyahu... obviously doesn't read the editorials of Le Monde or Liberation," wrote Eyal. "If he did, he'd know that he can't rely on Paris."

Trusting France to thwart Iran's nuclear programme would be "a grave mistake", he wrote. "French diplomacy has one central characteristic -- uncompromising flexibility."

"The (Israeli) attempt to hug and compliment a moment before the Geneva meetings was a bit too transparent," he continued.

"Possible contracts with Saudi Arabia and Gulf states are what could influence Paris. Meanwhile, they are doing so quite well, but Britain and Germany are putting huge pressure on Paris to not be a party-pooper."

Tsilla Hershco of the Bar Ilan university near Tel Aviv warned against expecting France to represent Israel's interests in negotiations with Iran, even if ties with Paris have warmed in recent years.

France "is also a European state and will take those interests into account, it has its own interests and its own issues", she told AFP.

According to Hershco, an expert on Franco-Israeli relations, "Netanyahu has more demands than France on Iran".

"It's a game of interests, sometimes they overlap... and sometimes they don't," she said.

Israel is the sole if undeclared nuclear power in the region, and along with world powers it suspects Iran of trying to acquire a nuclear weapons capability -- an allegation Tehran denies.

Netanyahu has warned Israel would do whatever it takes to prevent Iran from going nuclear, including a military strike.

On Sunday, his former national security adviser Yaakov Amidror told the Financial Times Israel was capable of launching an attack that would delay Iran's progress "for a very long time".

He noted that the Israeli air force had been conducting "very long-range flights" as part of preparations for just such a mission.

In an interview heavily promoted by Netanyahu's office, Amidror said the premier was "ready to take such decisions" as a unilateral military attack on Iran, if the need arose.