Israel’s Prime Minister Benjamin Netanyahu on Thursday described a reported Western offer to Iran — of “limited” sanctions relief in response to an Iranian agreement to start scaling back nuclear activities — as a “historic mistake.”

Addressing Israeli and Diaspora leaders in Jerusalem as a new round of talks on Iran’s rogue nuclear program got under way in Geneva, Netanyahu said, the proposals “on the table in Geneva” would “ease the pressure on Iran in return for ‘concessions’ that aren’t concessions at all.” He said Israel completely oppose these proposals, which would leave Iran with a capacity to build nuclear weapons.

“I believe that adopting [these proposals] would be a mistake of historic proportions. They must be rejected outright,” he added.

Sanctions had brought Iran to the brink of economic collapse, and the P5+1 countries have the opportunity to force Iran to completely dismantle its nuclear weapons program, the prime minister said. “Anything less than that” would reduce the likelihood of a peaceful solution to the crisis, he said, and Israel would always reserve to protect itself against any threat.

Later, Netanyahu angrily called the offer being discussed in Geneva, the “deal of the century” for Iran.

“If the news that I am receiving of the impending proposal by the P5+1 is true, this is the deal of the century, for Iran. Because Iran is essentially giving nothing and it’s getting all the air taken out, the air begins to be taken out of the pressure cooker that it took years to build in the sanctions regime. What we’re having today is a situation that Iran is giving up, at best, a few days of enrichment time, but the whole international regime’s sanctions policy has the air taken out of it. That’s a big mistake, it will relieve all the pressure inside Iran, it is a historic mistake, a grievous historic error,” Netanyahu told a visiting delegation of members of the US Congress on Thursday.

In an interview with Israel’s Channel 2 Thursday, visiting US Secretary of State John Kerry stressed the negotiators in Geneva were requiring Iran to “provide a complete freeze over where they are today.” He argued that it was “better” to be talking to Iran, and seeking to “expand” the time it would take Iran to break out to the bomb, than not to be talking to Iran, and have it continuing to advance its nuclear program. “We have not taken away any of the sanctions yet,” he said. “We will not undo the major sanctions regime until we have absolute clarity,” he said.

If Iran did not “meet the standards” required by the international community, Kerry said, it knew “worse sanctions” were in prospect, and even, as the “clock ticks down… there may be no option but the military option. We hope to avoid that.”

All diplomatic options had to be exhausted before a resort to force, he said.

As the talks kicked off in Geneva, the Iranian foreign minister said a deal over his country’s rogue nuclear program could be reached by week’s end, if all parties strove to reach that goal.

“If everyone tries their best we may have one,” Mohammad Javad Zarif was quoted by Reuters as saying. “We expect serious negotiations. It’s possible.”

Zarif made the comments to reporters after a preliminary breakfast meeting with European Union foreign policy chief Catherine Ashton.

A senior US official, speaking to reporters on Wednesday, said the six world powers of the P5+1 — the US, UK, France, Russia, China and Germany — were ready to offer “limited, targeted and reversible” sanctions relief in response to agreement by Iran to start scaling back activities that could be used to make weapons.

Iranian Foreign Minister Mohammed Javad Zarif at the United Nations, September 26,2013 (screen capture: Youtube/Youtube News)

Iranian Foreign Minister Mohammed Javad Zarif at the United Nations, September 26,2013 (screen capture: Youtube/Youtube News)

Israeli Energy Minister Silvan Shalom (Likud) said the offer was “unfathomable” and that it was a “grave mistake” to offer any easing of the sanctions pressure when the Iranians hadn’t done anything to dismantle their nuclear program. He said the nuclear program was seen by the regime in Tehran as its guarantee of survival, and that it was taking its cue from the summer’s Syrian chemical weapons crisis, when it saw that the West didn’t dare confront the relatively weak President Bashar Assad, even though he used chemical weapons against his own people 14 times.

Following Netanyahu’s cue, Israeli officials said they wouldn’t accept any compromise short of dismantling Iran’s nuclear research program.

“Israel… has learned that a proposal will be brought before the P5+1 in Geneva in which Iran will cease all enrichment at 20 percent and slow down work on the heavy water reactor in Arak, and will receive in return the easing of sanctions,” an Israeli official told AFP Wednesday, speaking on condition of anonymity. “Israel thinks this is a bad deal and will oppose it strongly.”

But in a nod to skeptics in Congress, the official emphasized that any economic relief given Iran could be canceled, should Tehran renege on commitments it makes in Geneva. She added that the six powers were looking to test the durability of any initial nuclear limits Iran agreed to by waiting — possibly for as long as six months — after such an agreement before any sanctions relief kicked in.

Iran and the P5+1 were set to begin two days of negotiations on Thursday in the latest round of talks aimed at allaying Western fears that Tehran is developing nuclear weapons. The United States is leading Western powers in demanding that Iran not only halt its nuclear development but cut back on its capabilities and stockpiles of enriched uranium and plutonium.

Times of Israel staff contributed to this report.