JERUSALEM (JTA) — Amid reports that a deal is near that would ease crippling sanctions on Iran, Israeli Prime Minister Benjamin Netanyahu called it a “historic mistake.”

An agreement on what is being called a first-step deal is expected by Friday, when the current round of negotiations in Geneva between Western powers and Iran is scheduled to end.

The P5+1 world powers, comprised of the five permanent members of the United Nations Security Council (Russia, the United States, China, France and Britain) plus Germany, began a new round of negotiations on Thursday with Iran in an effort to halt the Islamic Republic’s suspected nuclear weapons program.

Under the reported Western proposal, Iran would receive limited sanctions relief in exchange for an agreement to curtail nuclear enrichment activities.

“This is the deal of the century, for Iran,” Netanyahu told a group of visiting U.S. congressmen on Thursday. “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.”

Iran insists that its nuclear program is strictly for peaceful purposes.