"You will have probably, it's nearly sure, a period of tension in such a scenario", he said. And they stayed away for the entire speech, as we can assume that it would have broken their hearts to have heard kind words spoken by the French president about his American counterpart.
Macron's comments signal his inability to change Trump's mind about the deal during his US visit.
Oil prices were little changed in the wake of Macron's remarks.
A day after the French leader had put on a show of warmth and brotherly affection for Trump at the White House, his blunt speech prizing engagement over isolationism reinforced the French leader's emerging role as a top defender of the liberal world order.
In one of his final appearances of the trip, he expressed pessimism about the future of the Iran nuclear deal, saying he believed Trump may end up pulling out of the agreement.
That is sharply rejected by European officials, who are increasingly frustrated at spending time handling Trump's complaints rather than focusing on the deepening crises of the Middle East.
"We will continue to discuss the issue with the United Kingdom and France, but also with the US", Germany's Foreign Minister Heiko Maas told Reuters in Brussels, where he was attending a Syria donor conference.
The Pentagon chief said the administration was still considering whether the nuclear deal can be improved enough to persuade Trump it is worth preserving.
House Democrat Adam Schiff said that Macron had offered "more of a direct contradiction of the president than I was expecting".
"It is together that we will counter the proliferation in weapons of mass destruction, whether it is in North Korea or in Iran", Macron said.
The United States is not seeking to reopen or renegotiate the Iran nuclear deal, but hopes to stay in it to fix its flaws with a supplementary agreement, U.S. non-proliferation envoy Christopher Ford said on Wednesday.
Without explicitly giving his opinion about whether the United States should stick with the agreement, Mattis said that after reading the full text of the deal three times, he was struck by provisions that allow for worldwide verification of Iran's compliance. A state dinner, rich with ceremony and tradition, honors global leaders and pays homage to American customs.Macron will address the U.S. Congress on April 25 before his return to Paris.
The US president has called the JCPOA the "worst deal ever" and threatened to pull Washington out of the accord, which has the firm support of the entire global community.
Macron quickly realized that the chances were slim, sources say, and that Trump was looking for more than just a temporary fix that would buy more time, but the ability to say that he had changed the JCPOA itself. But we'll be talking about it.
Zarif repeated a warning that Iran would no longer be bound by the deal's limits if America withdrew.