In quitting the Iran nuclear deal President Donald Trump cast aside years of painstaking diplomacy and took the US stand-off with Iran into dangerous new territory.
America's European allies were dismayed by the decision, which fell even as London, Paris and Berlin were trying to negotiate a tougher accord to placate Trump.
And in Washington, even the sternest critics of the 2015 accord caught their breath as they digested the news -- and wondered what new escalation might come next.
Senior administration figures insisted that Washington is still determined to work with its humiliated allies to prevent Iran from developing a nuclear bomb.
But it is hard to square Trump's professed quest for a "new and lasting deal" with his scornful dismissal of the "decaying and rotten" original agreement.
The US leader is increasingly surrounded by hawkish voices like those of his new national security adviser, John Bolton, and his secretary of state, Mike Pompeo.
Their public position is that Iran can be forced by economic pressure into even greater concessions than those it grudgingly accepted under the 2015 deal.
But Trump's decision opened a rift with European allies that weakens the common front against Iran, and it is far from clear that Tehran can ever accept a tougher deal.
Some now say the logic of Trump's "maximum pressure" tactics leads not to a new quest for an accord but an attempt to crush Iran's already weak economy and to topple its regime.
"We have a president who is tough," Trump's personal attorney Rudy Giuliani told exiled Iranian opposition figures at the weekend. "We have a president who is as committed to regime change as we are."
But the 38-year-old Iranian revolution will not go down without a fight, and the risks of renewed regional war -- or a renewed nuclear arms race -- are growing alongside once taboo talk of regime change.
- Iraq debacle -
Celia Belin, a former policy adviser to the French foreign ministry and a visiting fellow to the Brookings Institution in Washington, says Europe will not reimpose its own sanctions on Iran.
"Europeans are slowly discovering Trump's 'hot potato' doctrine," she said, describing how Trump's habit of provoking unnecessary diplomatic battles then daring others to resolve them.
"However, it is unclear whether the Trump administration truly seeks a 'better deal,' or whether he and his administration are aiming for regime change," she warns.
So is Trump's true goal regime change? "Oh, I'm sure he would love that," says Rob Malley, a former adviser to president Barack Obama who helped negotiate the deal.
"I don't claim to be a Trump expert," Malley, now head of conflict resolution think tank the International Crisis Group, told AFP.
"But I'm sure that people around him -- he just hired or promoted two people, Bolton and Pompeo, who never made a secret of their view that the only way to change this issue is by changing the regime and taking military action."
The phrase comes with a lot of baggage in Washington, where the 2003 US campaign to oust Iraq dictator Saddam Hussein and change his regime is now widely regarded as a mistake.
Saddam's fall and the subsequent insurgencies in Iraq is seen as having encouraged the spread of jihadist groups and created an opening for Iran's influence to grow.
Trump himself says he opposed the war but some veterans of former president George Bush's administration -- notably the newly elevated Bolton -- defend it to this day.
And, in their attacks on the Iran deal, some see an attempt to rewrite history.
For these conservative war hawks, Tehran's rising regional influence is a byproduct of Obama's decision to drop sanctions, and not of Bush's destruction of Iran's enemy in Baghdad.
With Bolton in the Oval Office, these voices are getting louder, and with them the chance of a new deadly confrontation is growing.
President Donald Trump's national security adviser John Bolton has never made any secret of his desire to see Iran's Islamic revolutionary regime ousted