The U.S. debate over Syria in recent weeks indirectly helps answer a question that Turkey watchers have been discussing for some time: why has Russia been more effective at exerting leverage over Ankara than Washington?

Russia, quite simply, has been willing to use its Syria policy as a form of leverage with Turkey, adjusting it as circumstances require to either punish or reward Ankara. Washington, by contrast, has consistently made consequential decisions on Syria based on objectives that have little to do with Turkey.

Consider the course of the crisis that began when Turkey shot down a Russian plane in the fall of 2015. Turkey eventually apologized and sought reconciliation on Russian terms. This came after Russia imposed sanctions on Turkish exports and cut off tourist travel to Turkey. And yet what ultimately seems to have forced Ankara to seek reconciliation was not the need for sanctions relief but rather the recognition that achieving its goals in Syria – namely checking the advance of Kurdish forces there – required Russian consent. Before launching an operation in Jarablus in the summer of 2016, Ankara at the very least needed Russia to allow it access to the region’s airspace… access which Russia eventually granted.

Moscow, in other words, was able to exert leverage both because it was in a position to thwart Turkey’s goals in Syria by potentially shooting down Turkish planes and because it was willing to help Turkey achieve those goals even if it complicated Moscow’s relations with its Syrian, Iranian and Kurdish partners.

Washington, meanwhile, has made its relationship with Turkey a secondary priority in crafting Syria policy. The decision by sequential presidential administrations to support the YPG was made based on the desire for a rapid victory against ISIS. Assuaging Turkish concerns was, if not an after-thought, seen as necessary primarily to the extent it facilitated the counter-ISIS campaign.

Subsequently, the apparent decision to intensify support for the YPG in the beginning of this year was based on the desire to contain Iranian influence in the region with the resources most readily available there. More recently, when President Trump stated his desire to remove U.S. forces from Syria as quickly as possible, this was the result of his personal view of U.S. involvement in the Middle East more broadly. And if in the next six months Trump reverses this decision and decides to keep U.S. forces in Syria, it will likely be the consequence of concerns over prestige, credibility or posture towards Iran.

This is not to say, of course, that exerting leverage over Turkey should be a major factor in making policy toward Syria. But as long as it isn’t, that will shape the range of policy options that remain for Turkey. Whatever other economic carrots and sticks Washington debates using with Ankara, they will have less impact on the U.S.-Turkish relationship than the future of U.S. policy in Syria.