The US and Iran ignored a passionate plea from the Israeli prime minister to ditch their nuclear negotiations and held a third straight day of talks Wednesday seeking a framework deal in a few weeks.
US Secretary of State John Kerry and his Iranian counterpart Mohammad Javad Zarif were back at the negotiating table in the Swiss lakeside town of Montreux, and met for more than three hours Wednesday as a March 31 deadline for agreement on reining in Iran's suspect nuclear programme looms.
"We are working away," Kerry said as he strolled back to his hotel at the end of the talks.
In a dramatic speech to the US Congress on Tuesday, Israeli Prime Minister Benjamin Netanyahu called on the US administration to halt the talks which he warned "doesn't block Iran's path to the bomb. It paves Iran's path to the bomb."
He insisted the deal would leave Iran's nuclear capability largely intact and would turn the Middle East into a "nuclear tinderbox."
Israel itself is understood to have nuclear weapons but has never officially admitted to having such an arsenal.
Kerry did not watch the speech as he was thousands of miles away in the middle of negotiations with Zarif for the very agreement which the Israeli leader said would prove to be "a very bad deal."
Despite the political drama, US officials have shrugged off the address.
"I am not focused in the politics of this. I am not focused on the theatre," President Barack Obama said. "As far as I can tell, there was nothing new."
"On the core issue, which is how to prevent Iran from obtaining a nuclear weapon which would make it far more dangerous, the prime minister did not offer any viable alternatives."
And the Iranian foreign ministry denounced what it called Netanyahu's "continuous lie-spreading about the goals and intentions behind Iran's peaceful nuclear programme."
But the growing rapprochement between the United States and its old foe Iran after more than three decades of enmity has raised alarm not just in Israel, but also among US allies in the Gulf who remain wary of Iran's bid to spread its influence in the Middle East.
Kerry was set to fly later Wednesday to Riyadh where he will meet with Gulf Cooperation Council foreign ministers as well as new Saudi King Salman in a bid to allay their fears over the fledgling US engagement with Iran.
The growing threat of Islamic State (IS) group militants, who have captured a swathe of territory in Iraq and Syria, has however complicated the regional landscape, with Iran, a Shia Muslim country, taking on an increasing role in fighting the Sunni militants.
In a rare admission on Tuesday, the US military's top officer General Martin Dempsey said Iran's help in an Iraqi military offensive to recapture the Iraqi town of Tikrit could be "a positive thing" providing it did not fuel added sectarianism.
General Qassem Suleimani, the head of Iran's powerful Quds force, is reportedly on the ground with Shia fighters, armed by Iran, coordinating part of the offensive.
Officials in Baghdad say a 30,000-strong force has been mobilized to take back Tikrit.
Dempsey, the US joint chiefs of staff, said Shia militia account for about two-thirds of the force while Iraqi government army troops make up the remainder.
Saudi Arabia and other majority Sunni Arab and Gulf nations are leading members of the 60-strong coalition brought together by Washington to fight IS, and have already carried out airstrikes against IS in Syria.
And US officials insist that even if there is a nuclear deal with Iran, that does not mean they will turn a blind eye to the other activities of the country, still branded by Washington as the number one state sponsor of terrorism.
"If we have an agreement on the nuclear file, our view is that that is something that will contribute directly to regional stability, as well as global security and stability," a senior State Department official told reporters.
But he warned "regardless of what happens with the nuclear file, we will continue to confront aggressively Iranian expansion in the region, Iranian aggressiveness in the region."