President Donald Trump has made a fair share of blunders during his 14 months in office—so many, his critics claim, that it would take an entire week to compile a spreadsheet. First, there was the slapdash and wholly embarrassing rollout of the travel ban executive order, which caused mayhem across America’s major airports and browbeating from the courts. Then there was the abrupt firing of FBI Director James Comey, a decision that compelled the Justice Department to appoint Robert Mueller as special counsel to investigate the president’s ties to Russia. The forced resignations and dismissals of cabinet-level officers and senior White House staffers have only kept coming and have made the Trump administration look like an ignominious game of musical chairs. Finally, there is Trump’s personality and super-sized ego, which often grate on senior advisors who go home after 15-hour workdays wondering whether they’ll wake up the next morning without a job.

But all of these errors pale in comparison to a potentially monumental decision Trump will make on May 12. That’s the day Trump will determine whether Iran deserves another waiver from U.S.-crafted nuclear sanctions. Given the fact that the International Atomic Energy Agency (IAEA) and America’s own intelligence community have both verified that Tehran is meeting its commitments under the Joint Comprehensive Plan of Action (JCPOA), the decision to renew the waiver next month should be a straightforward and simple one. Unfortunately Trump does not see it that way: he has never liked the terms of the JCPOA, has long believed the agreement is an international humiliation for the United States and a triumph for the mullahs, and finds it a quintessential example of the stupidity and weakness of his predecessor. In some respects, this is a personal issue for Trump. If I were in office at the time, he says, I would have kept the sanctions on, brought Tehran’s economy to its knees, and forced them to dismantle all of their nuclear infrastructure, no ifs, ands, or buts.

To the State Department’s credit, U.S. diplomats are working hard to figure out a solution. Brian Hook, the chief of Foggy Bottom’s policy planning office, has been in negotiations with German, French, and British representatives for weeks, emphasizing that President Trump will throw the JCPOA in the dumpster if they don’t agree to additional sanctions on Iran’s ballistic missile program and regional destabilization. The problem with Hook’s effort, however, is that the Europeans have never truly bought into the argument that the nuclear deal needs improvement. In fact, European officials who have participated in talks with the administration don’t think they’ll amount to anything. Others have resigned themselves to the reality that Trump will pull out of the accord regardless of what Hook brings back to Washington. “We have given up hoping,” a senior European diplomat told The Guardian. “[Trump] wants to tick the JCPOA off, another thing he said he would do in the campaign…”

Experts in the American non-proliferation community are slightly more optimistic. I spoke to one who put Trump’s staying in the JCPOA at 50:50. Others around Washington are not so sanguine, assessing that the pullout is a sure thing. Hawks nesting at the American Enterprise Institute, the Foundation for the Defense of Democracies, and the Heritage Foundation—many of whom have been tapped by the White House for counsel on this issue—are salivating at the prospect of feasting on the dead JCPOA carcass.

Personally, I would put the odds of President Trump kneecapping the agreement at 75 percent. Yet regardless of the betting game, we should be clear about one thing: the day Trump begins reinstating nuclear sanctions on Tehran will be the day the United States creates a national security crisis. Destroying a non-proliferation agreement that, while certainly not perfect, has been verified time and again as successful would be a geopolitical mistake of the highest order. But to do so on the premise that Iran can be coaxed into negotiating with Washington in the future and starved into signing on the dotted line just like the German army did at Versailles is laughable.

If President Trump is serious about walking away on May 12, he should have no illusions about what he will be doing. He will have not only jeopardized what IAEA Director General Yukiya Amano has referred to as “the world’s most robust verification regime”—he will have done the impossible by making Iran look reasonable. President Hassan Rouhani, already under significant strain from his nation’s hardliners who never thought negotiating with the West was a smart idea, will take the blame. Tehran will view an abrogated JCPOA as license to wiggle out of nuclear restrictions entirely, either by kicking out IAEA inspectors or enriching higher quality uranium. At that point, the very people who are urging the White House to kill the deal in search of the unattainable will scream bloody murder. John Bolton, the incoming national security advisor, will pull out his 2015 “bomb Iran” New York Times op-ed and demand that Trump execute the military option. The United States will once again have to either accede to an Iranian nuclear weapons capability or risk a regional confrontation that would make the war in Iraq look like the invasion of Grenada.

Calling Defense Secretary James Mattis: on this issue, we need your intervention.

Daniel R. DePetris is a foreign policy analyst, a columnist at Reuters, and a frequent contributor to The American Conservative.