President Trump says he already has made a decision about whether his administration will find Iran in compliance with the nuclear agreement signed two years ago. If he has yet to share the direction he will head, he has been emphatic about his preference. At his recent speech to the U.N. General Assembly, he repeated his assessment of the deal, an “embarrassment to the United States,” one of the “worst and most one-sided transactions.”

So he doesn’t like it. Does he have room to wiggle out? Or strike a better deal?

Recall that Barack Obama did not negotiate alone with Iran. The agreement also involves China, Germany, Britain, France and Russia. These partners find no violations. The International Atomic Energy Agency agrees, reporting that Iran is meeting the terms. Iran has not broken the limits on its stockpiles of nuclear materials. It has not taken steps to advance its nuclear weapons program.

Nikki Haley, the U.S. ambassador to the United Nations, cites Iran balking at routine visits to its military bases. Yet such access isn’t part of the agreement. Neither are ballistic missiles, nor Iranian troublemaking in the Middle East. This is an arms control deal that would not have been possible if the talks included the range of concerns about Iran.

The president does have the option of declaring that the continued lifting of sanctions against Iran no longer benefits national security. Yet there is little evidence to support such a judgment. The idea is to prevent Iran from developing nuclear weapons, or adding hugely to the challenges facing a volatile region. The agreement puts off the pursuit for 15 years and then makes the task more difficult in subsequent years.

An American decision to back away wouldn’t just please Iranian hardliners. It would jeopardize relations with European allies who understand the agreement isn’t an ironclad guarantee but rightly see the value in buying time and exploring improved relations.

In return, Iran has gained a process for easing economic sanctions and access to its assets frozen abroad for decades.

The president has argued that the United States cannot abide by an agreement if it “provides cover for the eventual construction of a nuclear program.” Actually, an American withdrawal, or other steps weakening the deal, would open the way for Iran to accelerate plans for achieving nuclear weapons — leaving the fraught option of a military strike.

Congress requires the president to certify Iranian compliance every 90 days. The Trump White House twice has found Iran holding to the terms. What is different now? Practically nothing. This agreement reflects hard-won economic sanctions and persistent talks. Such a sequence would be almost impossible to replicate. Thus, the agreement shouldn’t be cast aside lightly, bringing such a one-sided result contrary to American interests.