President Donald Trump announces Tuesday afternoon that the United States...

President Donald Trump announces Tuesday afternoon that the United States will withdraw from the Iran nuclear deal. Credit: AP / Evan Vucci

In 2015 I voted against the nuclear deal with Iran. I cast my vote because the deal didn’t address Iran’s development of missiles or its supply of dangerous weapons to terrorist organizations on Israel’s border. I believe it was the right vote. I also believe that President Donald Trump’s unilateral withdrawal on Tuesday is the wrong move.

Here’s why.

The president has chosen to “go it alone” despite the fact that our key allies made progress on improving the agreement — especially in the areas of Iran’s missile program. Even the hawkish and conservative British foreign secretary, Boris Johnson, said our allies were “very close to a position that would address President Trump’s concerns and strengthen trans-Atlantic unity.”

Now that unity is fractured. With the reimposition of sanctions, our partners will face the choice of either agreeing with us, or, if they stay in the deal, facing our sanctions. If Trump finds a way to let Europeans off the hook on sanctions, then his decision to scuttle the deal leaves it intact. The decision becomes nothing more than the hollow delivery of a campaign promise with no substantive bite.

Of course, our partners could choose to pull out of the deal. That leaves the West as the ones who violated it, and the Russians, the Chinese, and Iranians themselves empowered to reciprocate. Iran might decide next week to “break the cement of Arak,” as one hard-line Iranian official said of a nuclear site closed under the agreement. When that happens, the call for a military response will grow, and we could find ourselves careening to another major conflict in addition to Afghanistan and Iraq. They were supposed to be easy. Our war fighters are still there.

There’s another consequence. I’m no fan of any Iranian regime that violates the rights of its citizens, transfers weapons to our enemies and exports terrorism. But Iran’s president, Hassan Rouhani, will appear weak for having made a deal that America dumped. Forces even more radical then he will exploit Trump’s decision and the miserable state of the Iranian economy. If the so-called moderates are toppled in Iran, expect replacements who provoke any conflagration they can to assert Persian pride and influence.

Trump reportedly objected to the fact that under the agreement, Iran can start to return to nuclear fuel production in 2030. But by ending the deal, Iran could resume its activities today, and have nuclear weapons by next summer. In fact, the 15-year time frame was not my rationale for opposing the agreement. I always believed a decade and a half was preferable to a year. It was the absence of provisions on missile testing and arming terrorists that compelled me to vote no.

And on those two critical challenges, we are now even worse off. Russia, China and Syria are empowered to allow Syria and Lebanon to be used as staging areas; the alliance opposing those actions — the United States, England, France, Germany and others — are at least for now divided and weakened. Any moderate influences in Tehran have lost credibility.

If Iran games this, it will announce that it will abide by the terms of the agreement as long as Europe holds up its end: doing business with Iranian companies and supporting Iran’s economy. On the surface, a U.S. withdrawal from a deal that Iran continues to respect may sound like a win. But it’s not. It leaves America practically alone in the world, with no diplomatic authority. Meanwhile, it’ll be business as usual with Iran, including diverting benefits to missiles and terrorist groups.

Trump’s decision has triggered a complex process. The accord does delay sanctions for several months before they bite. Perhaps the president is betting that the Iranians and others use that period to agree to a better deal out of desperation.

That may be his bet, but it’s one of the most dangerous gambles on the world stage.

Steve Israel, a former Democratic congressman from Huntington, is chairman of the Global Institute at Long Island University and author of the novel “Big Guns.”