THANKS TO the unanimous counsel of his national security team, President Trump appears to be edging away from his long- ­standing threat to junk the international accord that limits Iran's nuclear program. But it seems likely that he will embark on a dangerous and pointless game of brinkmanship with Tehran by refusing to recertify the deal to Congress. Such a declaration would be manifestly dishonest, and it could trigger a process that could cause the agreement to unravel. But it would spare the president from a duty he finds loathsome: certifying every 90 days that President Barack Obama's signature foreign policy achievement is intact.

The accord the Obama administration fashioned in 2015 is flawed. But there isn't much question that Iran is abiding by terms that drastically limit its stockpile of nuclear materials and make it virtually impossible to produce an atomic weapon in the next decade. The International Atomic Energy Agency has repeatedly certified Iran's compliance; according to Defense Secretary Jim Mattis, the U.S. intelligence community agrees. "Iran is not in material breach of the agreement, and I do believe . . . [it] has delayed the development of a nuclear capability," Joint Chiefs of Staff Chairman Joseph F. Dunford Jr. testified to Congress this week.

Mr. Trump nevertheless is said to be leaning toward "decertifying" Iran under legislation Congress passed. Doing so would not by itself rupture the accord; instead, it would give Congress a 60-day window to decide on reimposing sanctions. Decertification would require the administration to advance problematic claims contradicting Mr. Mattis and Mr. Dunford. It might protest that there have been no inspections of Iranian military sites; but then the United States has not provided evidence to the IAEA that such visits are needed. Mr. Trump could assert that the deal is no longer in the U.S. national security interest — but how, then, to justify subsequent waivers of sanctions?

Most proponents of decertification don't favor rupturing the deal through the immediate reimposition of sanctions. Instead, they say the administration should use the uncertainty as leverage to induce European governments to join the United States in pressing Iran for amendments. There are certainly improvements to be made: Sunset provisions will lift some of the restrictions on Iranian nuclear activity in eight to 13 years, and Tehran's continuing development of long-range missiles is not blocked by the pact. French President Emmanuel Macron, for one, has said he would be open to pursuing a follow-up deal.

But Iran is unlikely to agree to such modifications — at least not without major new concessions from the United States. If the Islamic regime continues to comply with the existing deal, the implicit U.S. threat — that it will follow decertification with withdrawal — will look hollow; in the absence of proven Iranian violations, Washington will have no European support. In any case, nothing prevents the Trump administration from enlisting U.S. allies in a new negotiating effort without the show of decertification.

The show, however, may be the point for Mr. Trump. Congress could spare him the pain of appearing to validate Mr. Obama's legacy by removing the certification requirement. Failing that, it should, at least, not compound his folly: It should not rupture a status quo that, for all its flaws, is preventing the eruption of another nuclear crisis.