The announcement comes in the immediate aftermath of a flurry of European diplomacy
. His decision may divide America from its European partners, France, Germany and the UK. And what happens next could further divide these nations, too.
If he opts to withdraw from the Joint Comprehensive Plan of Action -- as many diplomats fear he will -- it won't be the first time he has disregarded the wishes of his allies. Rejecting the Paris climate agreement, imposing trade tariffs and recognizing Jerusalem as the capital of Israel are just a few of Trump's detours from the desires of America's friends.
So, does Trump see the Iran deal not only as a lever to crack open the Middle East and reassert some American sway lost over the Obama years, but also as an opportunity to reshape relations with Europe?
Trump bridles at European unity. He has previously predicted that others will follow Britain out of the EU. And now, he could get to watch further fissures develop as Europeans scramble to salvage post-JCPOA business deals with Iran without earning Trump's ire.
The latest diplomatic intervention in DC saw Boris Johnson, the UK's Foreign Secretary, arriving in the final hours before we learn of Trump's decision.
In his opening salvo, an op-ed in the New York Times
, the British Foreign Secretary quoted Winston Churchill.
Churchill famously discoursed across the Atlantic with President Franklin Roosevelt, encouraging the US to support Britain it its battle against Nazi Germany.
Johnson appears to hope that invoking Churchill will persuade another US President to agree with the UK when it comes to defeating their current shared scourge: Iran.
If that's Johnson's plan, he won't be the first diplomat to tempt Trump's ego. France's President, Emmanuel Macron, did that last summer. He invited Trump for a Michelin-starred meal inside the Eiffel Tower amid the pomp of France's Bastille Day celebrations.
When Johnson appeared on "Fox and Friends" later on Monday, he was at pains not to antagonize Trump.
His first words: "The President is right to see flaws in it [the Iran deal] and he set a very reasonable challenge to the world: Iran is behaving badly."
But the bar was high. Macron beat him to that punch almost two weeks ago. While in DC, Macron declared: "We therefore wish from now on to work on a new deal."
German Chancellor Angela Merkel flew into DC a few days after Macron's visit.
Both appear to have concluded that Trump won't settle for the status quo on Iran.
Macron, Merkel and British Prime Minister Theresa May have exchanged several calls since then. They have indicated, for now at least, that they will stand by the Iran deal. However, they do appear willing to work with Trump on a tougher inspections regime and say that they share his concerns about Iran's destabilizing influence in the Middle East.
As Johnson arrived in Washington, the French and German Foreign Ministers were meeting in Berlin. Both sounded downbeat about averting Trump's anticipated decision. Germany's Foreign Minister Heiko Maas said: "We will see what the US decides, but we see no real alternatives."
Iran's Foreign Minister, Javid Zarif, thinks that the Europeans are being browbeaten by Trump: "This appeasement entails promises on a new deal that include matters we decided to exclude at the outset of our negotiations."
The leaders of Europe's three most powerful nations have all faced the indignity of a Trump moment in one form or another -- causing embarrassment at home. (Holding May's hand; not shaking hands with Merkel; flicking dandruff from Macron's shoulder.)
Each incident is a curious consequence of associating with a man lacking in nuanced diplomacy.
But what Britain, France and Germany clearly feel is that the consequences of Trump's Iran decision will be far greater than he realizes. "The world is safer with the treaty than without it," Maas said in Berlin.
Yet while these three European powers stand firm in apparent unity so far, their own actions -- and motivations -- also appear curious.
Macron, who was first to advocate changes to the deal following his meetings with Trump, then Merkel and then Johnson all appeared to reach the same conclusion.
It raises the question: are they acting in concert or each playing Trump their own tune?
By invoking Churchill, Johnson will have hoped to remind President Trump of the "Special Relationship" that Churchill kindled between the US and UK to overcome Hitler's threat.
It wouldn't be a stretch -- especially as the UK leaves the EU -- that in the face of "Le Bromance," Johnson is trying to hold onto Churchill's legacy as the most favored friend of the US.
But has Johnson considered that he -- along with the rest -- is being played?
By default or design, Trump is reshaping the world. His decision on Iran threatens to accelerate the process and render some of it irreversible.
By potentially upending the deal and straining European nations' individual business interests in Iran, is Trump leveraging rivalries, to diminish the EU's overall economic clout?
After all, as Merkel keeps reminding Trump, every time he talks to her about a trade imbalance with Germany, it's the EU -- not Germany -- that sets the trade relation with her country.
Having suspended steel and aluminum trade tariffs on the EU until a few weeks after his decision on the Iran deal, Trump may be adding another fact in European leaders' decision making.
Trump's instincts could be telling him that whatever it is he wants from Europe in the future, opening fissures over Iran might just help reach that outcome.