Experienced diplomats are warning that Donald Trump’s anticipated vote of no confidence in the Iran nuclear deal is a “crisis” whose impacts will reverberate to America’s detriment far beyond Iran.

Already, within the hallways of the State Department, anticipation over the imminent end of Secretary Rex Tillerson’s tenure is mixing with fear that a Tillerson replacement will help push the U.S. on a more bellicose path with Iran, whether the deal survives the year or not.

“Given what we’ve seen thus far, who the hell knows? It could certainly get worse,” a State Department official told The Daily Beast on condition of anonymity. “State could go from being underutilized and dormant, as it is now with Tillerson, to actively furthering really scary policies.”

Trump is expected to decline to certify Iran’s compliance with the nuclear agreement ahead of an Oct. 15 deadline, even though Iran has not violated the deal. He’s likely to give a speech on Friday denouncing Iranian support for terrorism and its development of ballistic missiles, both of which are outside the terms of the accord.

For the U.S. to sabotage the Iran deal in this way, particularly if Congress takes Trump up on reimposing sanctions, will lead allies, partners, adversaries and neutral powers to consider the U.S. “unable to take yes for an answer,” according to a former senior diplomat, diminishing American leverage on everything from North Korea’s nuclear crisis to the seemingly endless picayune complications of routine diplomacy like trade deals.

“It’s just another signal to the world that we don’t stand by our agreements, even those that are painfully, meticulously negotiated,” a second State Department official told The Daily Beast on condition of anonymity.

Walking away from the Iran deal would give “another bit of proof for the doubters” internationally that the U.S. can follow through on its commitments, the official continued. “Said questioning has been going on for a while.”

Giving just one example, “Russia and China are incredibly cooperative and flexible partners in negotiating and implementing the JCPOA,” said Jarrett Blanc, who until January was responsible for overseeing the implementation of the deal, known in diplomatic circles as the “J oint Comprehensive Plan of Action,” or JCPOA.

“If the U.S. demonstrates it is unable to take yes for an answer on the JCPOA, why should they play a constructive role with North Korea?” Blanc asked.

That question is already reverberating in foreign capitals—particularly in Europe, where the major power centers in London, Brussels, Paris, and Berlin are all parties to the Iran deal. European alarm at Trump was already acute when he pulled out of the Paris climate accords, a painstaking if insufficient effort at global cooperation to mitigate climate change.

“ State could go from being underutilized and dormant, as it is now with Tillerson, to actively furthering really scary policies. ”

To jeopardize the Iran deal will reinforce the view that “you can expect nothing positive from this administration, that the Americans have left the multilateral liberal order,” a European diplomat said.

Charles Kupchan, a former State Department and National Security Council official, expected the consequences for U.S. diplomacy will be “particularly high” in Europe, where foreign ministries pushed hard for the nuclear deal for years and have fanned out on Capitol Hill to urge Congress to protect it.

“Trump is already not a very popular person on the other side of the Atlantic. If he pulls out of the Iran deal, he will see his popularity in Europe decline even further and that will make it hard for European politicians to align with him across the board,” Kupchan said.

So Much for the Grown-Ups

The senior national security officials whom much of the world hopes will rein Trump in aren’t having much luck. Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff, recently stated that “Iran is adhering to its JCPOA obligations”; Defense Secretary James Mattis said that retaining the deal itself is in the broader U.S. national interest. Tillerson, for his part, is reportedly working with congressional Republicans to change legislation meant to cripple the deal politically, ostensibly to give the Trump administration a face-saving way to remain within it.

Mattis and Dunford’s places within the administration are secure. Tillerson, however, held a disastrous press conference on Thursday that highlighted his estrangement from the president, thanks to his non-denial that he has called Trump a “fucking moron.” A wave of news coverage has moved away from the long-standing portraiture of Tillerson as an unqualified steward of American diplomacy and is now portending his martyrdom.

Lately, the diplomats who will have to clean up the international mess that will come from Washington distancing itself from an Iran deal it spearheaded are viewing Tillerson’s likely successors nervously. Without revising their opinion of Tillerson as out of his depth, some consider United Nations Ambassador Nikki Haley and CIA Director Mike Pompeo as enthusiastic opponents of a deal designed to forestall an Iranian nuclear weapon for at least a decade.

Haley shepherded a 15-0 Security Council vote authorizing new energy sanctions on North Korea that stands as the administration’s only tangible diplomatic achievement thus far. (Supporters note that securing it required Haley to compromise, proving she can.) She subsequently gave a hardline speech attacking the deal that many considered an audition for Tillerson’s job.

As a Kansas congressman, Pompeo—whose closeness with Trump has prompted what one ex-intelligence official called “real concern for interference and politicization” of the CIA—told Fox News he couldn’t “think of a thing that has put America in a better position as the result of this deal.” (For good measure, John Bolton is also against the deal, though few think Bolton is as likely to take over State as Haley or Pompeo.)

Sigfried Hecker, a former director of the Los Alamos National Laboratory, is one of very few Americans whom the North Koreans have permitted to view their nuclear advancements. Hecker said that cancelling the Iran deal will “certainly make it much more problematic” to reach a diplomatic accord with Pyongyang.

The Iran deal provides more stringent inspections on Tehran’s nuclear efforts “than I ever thought possible,” Hecker writes in a forthcoming piece for Stanford University’s Center for International Security and Cooperation. He contextualizes Trump’s anticipated moves as following George W. Bush’s decision to abandon the 1994 Agreed Framework with North Korea, though there was a genuine case that North Korea cheated with at least the spirit of the agreement.

“The problem was that this killed the deal and the Bush administration was not prepared for the consequences,” Hecker writes. “Pyongyang withdrew from the Nuclear Nonproliferation Treaty, expelled the international inspectors and built the bomb. So, the Bush administration traded the potential uranium centrifuge path that would have taken a decade or so to build a bomb for the plutonium path that took less than a year. Walking away from the Iran deal now could similarly open the doors for Tehran to build the bomb.”

But undermining the Iran deal depends on a complicated minuet with Congress before it plays out internationally.

‘Ceding the Initiative to the Void’

In accordance with a law passed after the 2015 deal—not a provision of the deal itself—the administration has to certify every three months to Congress that Iran is complying with its terms. The Trump administration is widely expected to decline certification while not formally abrogating the JCPOA and punting to Congress, where GOP hostility to the deal has become right-wing catechism. In the absence of certification, thanks to the so-called Corker-Cardin law, a 60-day window to “snap back” sanctions on Iran will open.

Theories by Iran-watchers abound over whether Congress will reimpose sanctions or stop short of that to allow Trump to save face without blowing up the deal. Should Congress reimpose the nuclear-related sanctions that the JCPOA put in abeyance—something that requires only a 51-vote threshold in the Senate—the accord will begin a death spiral, as Tehran will be able to credibly argue that Washington destroyed the deal. Much depends on how specific Trump gets about what he wants Congress to do and how much pressure he is willing to place on senators to do it. (Yet right before this pivotal decision, Trump set fire to his relationship with Bob Corker, the chairman of the foreign-relations committee.)

Iran’s own hardliners are outwardly sanguine. State media quoted Mohammad Ali Jafari, commander of the Iranian Revolutionary Guards Corps, saying Trump’s “stupid behavior” would give Iran an “opportunity to move ahead with its missile, regional and conventional defense program.” These are the things Trump and other deal critics deride the JCPOA for neglecting.

But the Europeans are bracing for catastrophe. If the Iranians decide to walk away from the deal in response to Trump and renew production of highly enriched uranium for a bomb, the European diplomat said, continental capitals will be hard-pressed to reimpose their own sanctions, since the Americans and not the Iranians sparked the crisis. The diplomat compared it to a trap that allied governments did not know how to escape.

Blanc, the ex-implementation official at the State Department, said the punt to Congress would represent “ceding the initiative to the void,” itself a portend of American diplomacy after distancing itself from the deal.

“Non-certification is a terrible, terrible policy and even a crisis,” Blanc said, “but it will be nothing compared to the crisis if the U.S. actually fails to implement its JCPOA commitments to lift nuclear-related sanctions.”