As someone who has negotiated with Iran over the years perhaps more than any other U.S. diplomat, I disagree with those who argue that talks with Iran are akin to capitulation. I have seen little evidence that isolation has or will alter Tehran’s behavior in the right direction. Nor do I share the view that it is impossible to negotiate win-win deals with the Iranians.

Under the right conditions, which must include a hard-headed approach and tough actions to check Iran’s ambitions, Washington can benefit from bringing Iran into multilateral forums where the United States and its partners have the opportunity to narrow differences, create rules of the road and solve problems. Moreover, today we have little choice but to engage Iran on these broader issues, because no factor is shaping the order of the Middle East as much as the rivalry between Iran and its Sunni Arab neighbors, particularly Saudi Arabia and Turkey. This rivalry in turn is fanning sectarian conflict between Sunnis and Shiites across the Middle East, and increasingly, parts of Asia and Africa. And the wider chaos that has ensued continues to exact costs on our part of the world, as seen in terrorist attacks from San Bernardino to Brussels.

Gains by Iran’s Shiite proxies such as Hezbollah and the militias in Iraq and Yemen have led Saudi Arabia and Turkey to respond with expanded support for extremist Sunni groups. The heightened Shiite-Sunni conflict is undermining consensus and mutual acceptance among different communities in Iraq, Syria, Yemen and Bahrain.