The possible accord might not only tie Israel's hand in promoting its future warmongering policies in the region, but it could also have an unexpected knock-on effect and stymie U.S.-brokered negotiations between Israel and the Palestinians.

In a bitter outburst, Netanyahu denounced on Friday the contours of an Iranian agreement leaked to the media, once again putting himself in direct conflict with Washington.

"This is a very bad deal and Israel utterly rejects it," Netanyahu said as he headed into his third round of talks in just 48 hours with U.S. Secretary of State John Kerry.

Tellingly, Kerry did not appear in public with the Israeli leader on Friday and instead flew off in silence to Geneva to join talks between Iran and six world powers, including Russia, China and the European Union.

Despite his veiled threat, Netanyahu found it totally impossible to launch an attack on Iran. And right now, should Iran clinch an initial deal to relax tough economic sanctions in return for a partial pullback of its large nuclear program, Israel will face even tougher situation in the region.

"I can understand why Netanyahu is so furious," said Giora Eiland, a former Israeli national security adviser.

"A unilateral military option would have no real chance now. Not because we can't do it, but because it would be seen as moving against the whole international community," he told Reuters. "That is something Israel cannot afford."

NJF/NJF