In a carefully read 20-minute address at the American Enterprise Institute, Haley argued that the nuclear deal can't be considered in isolation.
Instead, Iran's history, its hostility toward the US and its behavior in the Middle East have to figure into Trump's calculus when he decides in October whether to certify if Iran is abiding by the deal, she said. And, Haley argued, both UN resolutions and US law should be considered as well.
"What I am saying is should he decide to decertify, he has grounds to stand on," Haley said. "It's very easy to just talk about compliance and the JCPOA," she said, referring to the deal's formal name, the Joint Comprehensive Plan of Action. "But there's so much more to the story that we need to be looking at," she added.
The deal, reached in July 2015 and implemented in January 2016, essentially eased nuclear related sanctions in exchange for curbs on Iran's nuclear program, some of which expire after a few years. Congress passed a separate law requiring the president to certify every 90 days that Iran is in fact complying with the deal, something Trump has done twice now.
Asked if the US would end up isolated for leaving a deal that has buy in from China, Russia, Germany, France, the UK and the EU, Haley said that European allies, who worked most closely with the Obama administration to craft the deal, understand the new US concerns.
She added that Washington's job wasn't to make sure allies were "comfortable."
"This is about US national security, this is not about European security," she said.
Haley's remarks appeared to draw a quick response from the French ambassador to the US, Gerard Araud, who tweeted a rebuke at the Trump administration's apparent attempt to move the goalposts on the Iran deal.
"The Iran deal is about the nuclear issue, nothing else," Araud tweeted. "So far, Iran is abiding by the commitments taken in this mutually agreed framework."
Haley rejected suggestions that decertifying the Iran deal could send a message to others involved in negotiations with the US -- particularly North Korea -- that Washington is an unreliable dealmaker, prone to back out of agreements as easily as it makes them.
Secretary of State Rex Tillerson is currently trying to pressure Pyongyang back to the negotiating table through an international "peaceful pressure" campaign.
"What's more important is that we let others know we will stay in a deal as long as it protects the security of the United States," Haley said.
She cited Iran's support for terrorism, proxy wars and malign actors, its weapons-smuggling and human rights violations -- subject to other US and international sanctions -- as reasons to pull back from the agreement.
"Everyone hoped the deal would make the Iranian government good people," Haley said, "but no one looked at the history of Iran, no one looked at all the past aggressions they have shown."
When limits on Iran's uranium enrichment or centrifuge production expire, Iran may be able to send a nuclear warhead to the US, as North Korea can now, Haley said. "What if we just gave them 10 years, and all the money they wanted to do what they want to prepare for, when that 10th year hits and they start nuclear war?" Haley said.
A congressional aide, speaking on condition of anonymity to discuss Haley's speech, said that if the President chose not to certify Iran's compliance, "they would need to be very clear with Congress about what Iran has done to not deserve certification."
"Thus far, at least to us, there has been no evidence produced. Just all the innuendo in the press and from the President himself," the aide said.
The US law requiring the President to certify compliance also requires the administration to brief Congress on the specific technicalities of how Iran is in violation, the aide said.
Maryland Sen. Ben Cardin, the top Democrat on the Senate foreign relations committee, said it would be a mistake for the US to take unilateral action to leave the Iran agreement, especially for political purposes.
"It's a factual determination that the administration has to make as to whether Iran is in compliance with the agreement or not," Cardin said. "That's a factual determination -- it's not a political determination."
But Senate foreign relations chairman Bob Corker of Tennessee said that Haley was merely describing mechanisms of the certification law that Congress passed.
"That's the way the legislation is written, that under certain circumstances it comes Back to the House and Senate," Corker said. "I didn't think it was anything groundbreaking in what she said."
The former South Carolina governor denied that her speech was meant as a signal of what's to come. "I'm not going to prejudge in any way what the President is going to decide next month," Haley said. "While I have discussed it with him, I do not know what decision he will make. It is his decision to make, and his alone."
Still, she crystallized the message that administration officials and those close to the White House have been conveying in recent months. "The entire world thinks the JCPOA is untouchable," Haley said, "but it's not."