World War 3? An unstoppable surge of new tension in the Middle East? An explosive arms race? Or just more of the same old high-stakes reckless game-playing that has plagued the region for decades, if not centuries?
After years of fractious negotiations, a pact was finally signed in 2015 between the US, Britain, Germany, France, Russia, China and Iran under which Tehran agreed to rein in its controversial nuclear programme in return for an easing of tough economic sanctions.
Trump has castigated Barack Obama’s administration for agreeing to what he terms an “insane” and “ridiculous” accord.
He says the pact does not address other serious Western worries about the Islamic republic’s growing regional influence, including itsballistic missile programme and its support for armed groups in Yemen, Lebanon and Syria.
In January Trump stressed that unless the pact was widened to address his concerns about Iran’s true intentions in the Middle East, he would not re-certify it as he is scheduled to do on May 12.
The consequences of Trump walking away from the deal are so unpredictable that an array of alternative scenarios are possible.
No one listens any longer to the doomsayers, who have been warning of a final showdown between good and evil in the Middle East for centuries.
So cross out the World War 3 scenario.
But there is no doubt that a US decision to bail from the deal would dramatically ramp up tension in the already volatile region.
German Foreign Minister Heiko Maas tweeted: "The situation in the Middle East would become much more dangerous without the nuclear agreement with #Iran."
The worst case scenario would see Iran itself pulling out of the accord, known as the Joint Comprehensive Plan of Action (JCPOA), resuming uranium enrichment and developing nuclear weapons, which neither the US nor Israel would tolerate. Military strikes would follow, with unimaginably dire consequences.
Most observers believe that Tehran won’t ditch the deal as the suspension of sanctions has allowed foreign capital to flow into Iran and given the country a gateway back into the international community after years of isolation.
But, with powerful hardliners at odds with the reformists presently in power, nothing is certain when it comes to Iran.
Foreign Minister Javid Zarif warned this week: "If the United States officially withdraws from the JCPOA, the immediate implication would be that it would free Iran of any obligation to remain."
If Iran does follow suit, inspections of Iran’s nuclear sites by UN inspectors would halted and the world would be back to guessing just exactly what the Islamic republic is up to and what are its nuclear capabilities. This would in itself be a deeply destabilising factor in the Mideast.
A Trump withdrawal would also cause an immediate rift between the US and its European allies, who are adamant that the nuclear deal cannot be renegotiated.
Germany, France and Britain would suddenly find themselves in the same camp as Russia and China against the US.
Two other scenarios are possible:
1. The US stays in but the wording of the pact is revamped. This is seen as the most likely outcome, despite Iranian President Hassan Rouhani stressing that Iran would not accept "to add or omit even a simple sentence" from the deal.
2. The US pulls out, Iran stays in and the three European powers do their best to protect the accord. This is seen as second most likely outcome.
France and Germany meanwhile are using all their political wiles to try to dissuade Trump from pulling out of the deal.
But the French leader’s efforts appeared to have been in vain, telling journalists later that he thought there was a "big risk" Trump would bail.
On Friday it was German Chancellor Angela Merkel’s turn to try to woo Trump – not only on the Iran nuclear deal, but also on the issue of trade tariffs.
But there was no hugging and only a peck on the cheek for Merkel. During a rather frosty news conference with Trump, the chancellor defended the deal as a “building block” but acknowledged that it was “anything but perfect – it will not solve all the problems with Iran”.
Trump is keeping his cards close to his chest and we are only likely to know after May 12 whether the combined efforts of Macron and Merkel made any impact at all.
"Nobody knows what I'm going to do on the 12th," Trump told reporters this week.
Yes, nobody knows. Probably at this stage, not even the erratic president himself.