First, the French president and then the German chancellor visited the White House last week. Both Emmanuel Macron and Angela Merkel pitched President Trump on the value of sticking with the Iran nuclear agreement. How did it go?

According to reports, Macron appears resigned to the president pulling out of the deal “for domestic reasons,” likely by May 12, the deadline for the most recent periodic review. Candidate Trump repeatedly described the agreement as a “terrible, one-sided … horrible deal.” He still does. So he may be set to keep a promise, and now his cast of advisers includes prominent voices who share his harsh assessment, John Bolton, the national security adviser, and Mike Pompeo, the secretary of state.

Macron, Merkel and others have argued that the president can work to make the agreement better, seeking to expand its reach into areas, such as ballistic missiles, that negotiators earlier left off the table. Merkel provided a helpful insight when she called the deal “one piece of a mosaic.”

The larger objective is constraining Iran in a turbulent Middle East where it has gained advantages, especially as a result of the civil war in Syria. The nuclear agreement stands as the one concrete restraining mechanism. A strong verification regimen reports that Iran has held to its commitments, putting off for a decade, and possibly more, its pursuit of nuclear weapons.

And if Iran breaks from the deal? Tough sanctions and other isolating measures would be applied. More, the response would be collective, the United States acting with its partners, and thus with clear moral authority not available if the White House just bolts on its own.

Part of the mosaic concept goes to the reality that Washington entered the agreement along with others, including Russia and China. All recognized the larger danger in Iran continuing its pursuit of nuclear weapons, or the likely result if the president withdraws from the agreement.

Break from the deal, and rallying partners around something new promises to be most difficult. Might there be military options? Here, the president has sent signals via his response in Syria, willing to launch narrowly conceived missile strikes yet staying away from a prolonged and messy military commitment.

Perhaps that posture will change, though it also flows from campaign pledges.

The nuclear agreement isn’t the product of unrealistic hopes, that somehow it would address fully the challenges posed by Iran. It isn’t one-sided. Iran essentially gains access to frozen financial assets in exchange for halting its nuclear program.

The deal is something upon which to build. It addresses the nuclear question and allows Washington and its partners to move forward on other items regarding Iran. In that way, the message from France and Germany was simple enough: The next step should not be a wholly unnecessary nuclear crisis, driven by a decision that misses what brought the single achievement in constraining Iran, countries working together.