NATO entered uncharted territory on Tuesday when one of its members, Turkey, shot down a Russian warplane. There is an urgent need for Washington to bring both sides together to avoid World War Three.Details are still emerging to corroborate Ankara’s insistence that the jet had been repeatedly warned and violated Turkish airspace near its border with Syria. What is clear is that this incident has been a long-time in the making given the precipitous build-up between Ankara and Moscow over conflicting Syria policies. Since Russia started flying its warplanes over Syria in support of Assad, it has repeatedly violated Turkish airspace.Despite hopes of a “grand coalition” forming in the wake of the Ankara, Sinai, and Paris bombings claimed by the so-called Islamic State, now there is an urgent need for de-escalation to salvage what little is left of peace and stability in the Middle East.Moscow’s immediate accusations of Ankara’s “back-stabbing” and support for Islamic State followed by Russian President Vladimir Putin’s warnings of “serious consequences,” highlight just how high the stakes in Syria are for all parties involved. Hopes that the spillover effects from Syria could be contained are now dashed.Turkey’s support of their ethnic brethren, the Turkmen of the northern Syrian region where the Russian pilots likely ejected, will only further complicate the situation on the ground. Given the fissures among the Kurds, Islamists, and rebel groups fighting Syrian President Bashar Assad and his Russian and Iranian supported forces, there is no hope of victory on the ground. To avoid further confrontation in the air and to prevent Russia from any retaliatory action, the North Atlantic Treaty Organization must re-affirm its support of Turkey and call for an immediate no-fly moratorium over Syria.America’s unique role as mediator between its transatlantic allies in Ankara and rivals in Moscow has never been timelier. Many in Washington had hoped that in the wake of the recent attacks on Paris and progress at last week’s G-20 summit in Turkey, a common approach to defeating Islamic State would develop. Even after their own bombings in their capital, Ankara, Turks are wary of outside intervention in the region that doesn’t remove Assad as they fear they might be left to pick up the regional pieces.Turkey already hosts the world’s largest number of refugees and the Syrian civil war has become entangled in Ankara’s decades-long struggle against Kurdish militants, some of whom are now supported by the United States. Now, the best that can be hoped for is that Ankara and Moscow will pragmatically focus on their interdependence and the costliness of further escalation to avoid letting Syria drag them into open warfare. Bringing Russia and Turkey to the same table must now be part of a broader regional political compromise that centers on Assad’s future. It will be difficult, but not impossible, to devise an exit strategy that contains Assad in the short-term, while allowing for the long-term transition of his regime. Any such solution must permit Moscow and Tehran to save face and the various coalitions to come back together. Given Turkey’s calls for “regional solutions to regional problems,” Ankara should be supported by its transatlantic allies in becoming a non-sectarian regional leader. That must include applying pressure on Arab and Sunni powers to provide critical development assistance to counteract Iranian and Russian influence in Damascus. Concurrently, Moscow must be assured that its Mediterranean foothold in Latakia will be maintained in any post-Assad Syrian outcome.Due to contentious electoral politics earlier this year, Ankara had been paralyzed. But Putin may have misjudged Turkish President Recep Tayyip Erdogan, whose ruling AK Party’s mandate is now clear: stability through strength.Saving face for both leaders, who once considered each other friends, will be critical and best facilitated by calls of restraint from President Barack Obama and France’s leader, Francois Hollande. Any shuttling between Washington and Moscow to discuss a grand coalition against Islamic State now must include Turkey to have any hope of success.Pitting the region’s largest economy, military/intelligence power, and only NATO ally, against Russia is a recipe for further Middle Eastern disintegration. To avoid further war, all sides must focus on the common interest in de-escalating the situation. They must focus on their common enemy - Islamic State - which must be military defeated to facilitate a strategy for politically reconstituting Syria and Iraq as sovereign states. Obama has studiously avoided repeating President George W. Bush’s actions in Iraq, but now America must exert itself to prevent further war.Power vacuums in the heart of the Middle East have almost always led to worse outcomes. Preparing now for a peace that the region will own is critical to all parties and should be an area of mutual agreement. A regional summit called by NATO to include Ankara and Moscow will allow both sides to put this week’s incident behind them, and help all involved focus on the common enemy.Joshua W. Walker is a transatlantic fellow of the German Marshall Fund of the United States.