Easing pressure on Iran over its nuclear programme would be an "historic mistake," Israeli Prime Minister Benjamin Netanyahu warned on Monday, a day before world powers resume talks with Tehran.

"It would be an historic mistake to ease up on the pressure now, a moment before the sanctions achieve their objective, and particularly now, we must not give up on them but continue the pressure," Netanyahu said at the opening of the Israeli parliament's winter session.

His stark warning was an unvarnished appeal to the West to avoid making any concessions to Iran's new President Hassan Rouhani, whose conciliatory tone has raised hopes of a breakthrough in the decade-long dispute over Tehran's nuclear programme.

As the parties readied to meet in Geneva for two days of talks starting on Tuesday, Israel's premier sought to drive home the message that any move to soften the economic sanctions would be handing a victory to Tehran's hardliners.

It was the sanctions, Netanyahu said, that had brought Iran's economy "close to breaking point" and forced a tactical change in Iran's plans to develop nuclear weapons, prompting Tehran to offer to carry out a "meaningless change" in its nuclear programme.

"Iran can quickly enrich uranium from a low level of 3.5 percent to a high level of 90 percent.. (and) is willing today to give up on the enrichment to the interim level of 20 percent -- which is no longer important for it -- in exchange for a significant easing of the sanctions," he charged.

"This means Iran is willing to give very little and receive a great deal," he said, warning that accepting such a deal could bring about "the collapse of the entire regime of sanctions."

Any move to let up on Iran would only strengthen its "uncompromising elements" and its supreme leader, Ayatollah Ali Khamenei, "will be perceived as the winner," Netanyahu said.

The Israeli premier has said Iran must meet four conditions before there is any move to ease the sanctions regime: halting all uranium enrichment; removing all enriched uranium from its territory; closing its underground nuclear facility in Qom; and halting construction of a plutonium reactor.

Israeli Intelligence Minister Yuval Steinitz also called on world powers to maintain the pressure of sanctions against Iran, saying the Islamic republic must be presented with an ultimatum.

"The dilemma will be crystal clear to them (the Iranians), that if they want to save their economy, they need to give up their nuclear project," he told reporters.

Iran has so far refused to say what it might offer in return for relief from EU and US sanctions, but has made clear it will not accept any demand to hand over its stockpiles of enriched uranium.

"We will negotiate about the volume, levels and the methods of enrichment but shipping out the (enriched) material is a red line for Iran," Iran's deputy foreign minister Abbas Araqchi, who is representing Tehran at the talks, said on Sunday.

The Geneva meeting will be the first such talks since Rouhani took office in August, pledging to engage constructively to resolve the nuclear question and ultimately to secure the lifting of crippling Western sanctions.

The West has responded positively to Rouhani's overtures, sparking fears in Israel that the sanctions could be significantly softened, or even ended.

Israel's President Shimon Peres warned on Monday that the world must not judge Iran by its words but by its actions.

"The sweet words of Rouhani are pleasing to the ears of all who are tired of (Mahmoud) Ahmadinejad's lack of restraint," he said of Iran's belligerent former president.

"But it is up to the word to judge Iran by its actions and not by its declarations... Actions should be credible, transparent, not partial and not delayed," he told MPs at the parliamentary ceremony.

Israel has refused to rule out a military strike to prevent Iran from going nuclear, with Netanyahu telling the UN General Assembly earlier this month that the Jewish state would act unilaterally if necessary.