Turkey Russia Iran

Iran's President Hassan Rouhani speaks during a joint news conference with Russia's President Vladimir Putin and Turkey's President Recep Tayyip Erdoga in Ankara, Turkey, Wednesday, April 4, 2018. (AP Photo/Burhan Ozbilici)

In order to put pressure on our European allies, President Trump has threatened to withdraw on May 12 from the Obama-era nuclear agreement with Iran unless the allies support needed changes to the deal. The allies are balking, but the president’s approach may yet yield tougher sanctions before the deadline.

The key changes would address glaring deficiencies in the agreement, which allows Iran the opportunity to resume full development of nuclear arms by 2030, the right to continue developing missiles as delivery vehicles for nuclear weapons, and the right to refuse inspections of military facilities that, in the past, have been the locations of secret nuclear development activities.

Our key European allies, for commercial reasons, seek to maintain the current agreement, saying that if they support the changes demanded by Mr. Trump, Iran will simply resume its nuclear weapons development program this year instead of waiting a decade.

In particular they object to revoking the sunset provisions of the agreement, which gradually relieve Iran of its obligation to restrict nuclear development activities and allow inspections by the International Atomic Energy Agency.

They also reportedly object to aiming sanctions at Hezbollah, the Iranian proxy militia in Lebanon. But they appear to be ready to impose sanctions on Iran’s missile programs.

The risk they run, if Mr. Trump holds to his “snap back” sanctions on Iran that were suspended under the current agreement in the absence of the changes he demands by May 12, is that those sanctions would fall on any European businesses that trade with or supply credit to Iran. In effect Mr. Trump is asking the allies to choose between developing commercial ties to Iran and continuing their much larger commercial ties to the United States.

Mr. Trump has sent a message to Europe in choosing a new secretary of state, Mike Pompeo, and a new national security adviser, John Bolton, both of whom are strong advocates of the changes Mr. Trump seeks in the Obama-era Iran agreement.

If Europe continues to balk, an alliance crisis could be the outcome.

But with allied support there may yet be a way for Mr.Trump to get most of what he wants on Iran without giving up his demand for permanent denuclearization of both Iran and North Korea or completely abandoning the Iran deal.

That path would include new sanctions on Iran for missile developments in defiance of U.N. resolutions, plus the continued shadow cast by the threat of renewed U.S. sanctions.

That shadow has already prevented Iran from realizing the full potential of expanded trade with Europe because many banks are reluctant to finance Iran deals fearing that they might face U.S. reprisals.

Such an outcome would give Mr. Trump a partial success and put Iran on notice that further efforts at missile development or destabilization of the Middle East could trigger much harsher punishment, all without the cost of a major breach with France, Germany, Britain and the European Union.

And it would enhance the U.S. bargaining position in upcoming talks with North Korea on denuclearization.