Turkey and the West need each other to influence the future of Syria. The United States and Europe need to shun the idea of sanctioning Turkey and follow a results-oriented policy with Ankara. Sanctions will cost the United States and Europe the ability to work with the only NATO nation bordering Syria. It will have ill-fated consequences for a lasting and sustainable settlement of the refugee problem and a more effective counterterrorism policy to address the challenge of the remaining foreign fighters in Syria.
And Turkey will lose the ability to leverage the support of its Western partners for its regional objectives. Turkey will be politically and diplomatically isolated in the negotiations for a political settlement in Syria, where Russia and Iran will play a major role.
Russia has already emerged as the most powerful piece on the Syrian chessboard. Moscow rapidly facilitated a deal between Mr. Assad’s regime and the Y.P.G., which allowed the Syrian Army — for the first time since 2012 — to take control of significant towns such as Manbij in northern Syria, which had been controlled by the Y.P.G.
The outcome is perfectly in line with Russia’s envisaged endgame — to ensure that Mr. Assad extends territorial control to all of Syria. And in the meantime, Moscow intends to force Turkey to reconcile with Mr. Assad.
Instead of sanctions, the United States and Europe need to devise a mutually agreed plan of action with Ankara that would incorporate three major elements. First, they need to acknowledge that the policy of support to the Y.P.G. has ended; no long-term constructive engagement with Turkey can work otherwise.
Second, Turkey, the United States and Europe should restart a strategic dialogue to foster a common approach to the constitutional order and security arrangements for a new Syria. Otherwise, Moscow and Tehran will be in increasingly strong positions to reshape the regional order.
And third, Turkey’s western partners should incentivize Ankara to return to an agenda of domestic political reforms, which would also tackle the country’s longstanding Kurdish problem.