WASHINGTON — THE Iran nuclear deal offers a long-term solution to one of the most urgent threats of our time. Without this deal, Iran, the world’s leading state sponsor of terrorism, would be less than 90 days away from having enough fissile material to make a nuclear bomb. This deal greatly reduces the threat of Iran’s nuclear program, making Iran’s breakout time four times as long, securing unprecedented access to ensure that we will know if Iran cheats and giving us the leverage to hold it to its commitments.

Those calling on Congress to scrap the deal argue that the United States could have gotten a better deal, and still could, if we unilaterally ramped up existing sanctions, enough to force Iran to dismantle its entire nuclear program or even alter the character of its regime wholesale. This assumption is a dangerous fantasy, flying in the face of economic and diplomatic reality.

To be sure, the United States does have tremendous economic influence. But it was not this influence alone that persuaded countries across Europe and Asia to join the current sanction policy, one that required them to make costly sacrifices, curtail their purchases of Iran’s oil, and put Iran’s foreign reserves in escrow. They joined us because we made the case that Iran’s nuclear program was an uncontained threat to global stability and, most important, because we offered a concrete path to address it diplomatically — which we did.

In the eyes of the world, the nuclear agreement — endorsed by the United Nations Security Council and more than 90 other countries — addresses the threat of Iran’s nuclear program by constraining it for the long term and ensuring that it will be exclusively peaceful. If Congress now rejects this deal, the elements that were fundamental in establishing that international consensus will be gone.