The New York Times | Roger Cohen: If President Trump decertifies the Iran nuclear deal this week, as�seems likely, �it will show total disrespect for America�s allies,� Wolfgang Ischinger, the former German ambassador to the United States, told me. That�s the least of it. This � and I know competition is stiff � would be the rashest, most foolish act of the Trump administration to date.


The president�s refusal to certify an accord his own defense secretary, James Mattis,�says Iran is upholding, and is in the American national interest, would send a strong signal that the United States has become a bait-and-switch power whose word is worthless.


It�s America�s word as solemn gage that has underwritten global security since 1945. Goodbye to all that.


Uncorked, Senator Bob Corker, the Republican chairman of the Senate Foreign Relations Committee, has�grown bubbly. He�s compared Trump�s White House to �an adult day care center� in which only the likes of Mattis are keeping the child-sovereign�s tantrums from causing disaster. He�s suggested that, through infantile recklessness, Trump could set us �on the path to World War III.�


Exhibit A in this pattern of puerility would be the decertification of a multilateral deal that is working and�is supported�by China, Russia, Britain, France and Germany, powers with which Trump may even have a passing acquaintance.


Bait and switch, I said. The accord is a nuclear nonproliferation deal, not a grand bargain with Iran. It was concluded, as most breakthrough diplomatic accords are, with a hostile power. It was designed to curb the potential threat from the Islamic Republic, not change the nature of the regime overnight. It was about centrifuges, not Iranian support for Hezbollah; enriched uranium, not Iran�s terrible human rights record. It represents a difficult compromise between two countries � the United States and Iran � whose accumulated grievances stretch back decades but whose unyielding confrontation benefits neither.


Iran�s nuclear program was pitched into reverse by the agreement after a decade of rapid development. The number of centrifuges was slashed. Iran�s uranium stockpile was all but eliminated; enrichment levels are capped at 3.7 percent, a long way from bomb grade; outside inspection by the International Atomic Energy Agency is rigorous. The IAEA, like Mattis, has found that Iran is in compliance.


Would it have been nice if Iran had been persuaded to dismantle its nuclear program and its scientists induced to consign their mastery of the nuclear fuel cycle to amnesiac oblivion? Sure. Dream on. Diplomacy takes place in the real world, as those mouthing off about North Korean nuclear dismantlement will discover. It involves trade-offs equally painful for both sides that produce an imperfect outcome better than the alternative.


(If anyone�needs reminding�of the alternative, North Korea has nukes. Iran does not � and is now further from one than it was. One of the extraordinary aspects of Trump�s caprice is his apparent willingness to open a second nuclear front, like some loony generalissimo who wakes up feeling an Asian conflagration is insufficient, a Middle Eastern one is needed, too.)


Thanks to Dexter Filkins at The New Yorker we have a�verbatim account�of Secretary of State Rex Tillerson�s first encounter last month with the Iranian foreign minister, Mohammad Javad Zarif. Tillerson is an ineffective secretary of state whose major contribution to truth-telling has been to call his boss, Trump, a moron. Still, as long as he�s around, he�s beholden to the Trump line on Iran, whatever his own reservations.


So Tillerson tells Zarif: �No one can credibly claim that Iran has positively contributed to regional peace and security.� This is true, but irrelevant to the nuclear deal. He tells Zarif that lifting sanctions under the accord �has enabled Iran�s unacceptable behavior.� This is untrue and so by definition irrelevant. He says of Iran and the United States, �the relationship has been defined by violence � against us.� The violence has gone both ways, and this is irrelevant.


Bait and switch: Imagine if Iran said it planned to rip up the nuclear agreement because the United States elected a Saudi-loving, Iran-hating president in Trump; and his dancing with the Saudi royals, combined with his Qatar derangement syndrome, had not �contributed to regional peace and security.�


Filkins writes of the encounter: �An aide to Tillerson later told me, �It was one of the finest moments in American diplomacy in the last fifty years.� �


I am paid to produce words. I regret that this sentence renders me speechless.


Of course, a Trump refusal to certify may not unravel the deal, but it would put it on life-support, as well as doing lasting damage to American�credibility.


The Republican-controlled Congress may not reimpose sanctions � a step that would kill the accord � or take other legislative action to scuttle it, but Trump will already have done enough damage to make any nation question why it should conclude a deal with the United States. Only Trump could contrive to cede the moral high ground to Iran.


Trump will also have made the Middle East more dangerous, reinforced Iranian hard-liners, angered allies and done a disservice to Israeli security. He is in a class of his own.