Aside from the Islamic State, the most urgent threat to Turkey is the territorial expansion and consolidation of the Kurdish People's Protection Units (YPG) and Democratic Union Party (PYD). Turkey has essentially been trying to kill two birds with one stone by planning a military intervention in northern Syria that would push the Islamic State from the border while also dividing and containing YPG-held territory. Since Turkey downed a Russian Su-24 in November 2015, however, Russia has effectively blocked Turkey's plans by threatening to target Turkish assets operating in Syrian territory.
So, Turkey is stuck. And the longer Turkey is stuck on its side of the border, the more YPG forces can take advantage of the situation by incrementally grabbing more territory along the Turkish border. To curb Kurdish expansion, Turkey has tried to persuade the United States to use non-Kurdish rebels in the north to lead an offensive against the Islamic State, but that strategy has been only somewhat effective. (As a result, the United States has been tempted to work with Kurdish elements of the Syrian Democratic Forces to maintain sufficient momentum in the fight against Islamic State but has refrained thus far.) Moreover, as Russia and the United States attempt to end the Syrian civil war through peace negotiations, talk of federalism in Syria is gaining momentum, and Turkey does not want a power transition in Syria to create a de facto Kurdish federalist state. Hence Turkey's dialogue with other capitals in the region, especially the ones that do not want Kurdish independence to undermine their territorial integrity. This is a point on which Ankara, Tehran and Damascus, as well as Baghdad, can agree, and Turkey is hoping to use this common ground to reach some level of understanding with the al Assad government.
But cooperation from Syria and its Iranian benefactors will not come cheap. The Syrian government knows it has little chance of being able to restore the control it once had over the entire nation and is focused instead on consolidating its hold on the country's core. Even though the Syrian government shares an interest with Ankara in preventing Kurdish federalism, containing Kurdish expansion in the north and east does not currently rise to the top of al Assad's list of priorities. In fact, Syrian government forces have largely avoided major confrontations with the YPG and can use the Kurds to pressure Turkey in the near term. If Turkey's concern over the Kurds escalates to the point that Ankara comes to the negotiating table, as it appears to be doing now, the al Assad government can use the opportunity to set some boundaries on Turkey's activities in Syria.
According to Stratfor's source, Turkey is asking the Syrian government to cooperate in containing the YPG and PYD. In return, the Syrian government is demanding that Turkey curtail its interference in the Syrian conflict. Unsurprisingly, the talks have been inconclusive. Even if the Syrian government reached an agreement with Turkey to work against the Kurds, Syrian forces are already stretched thin as they try to hold territory and regain key cities such as Aleppo while keeping the Islamic State at bay. And so long as Damascus remains vulnerable, Turkey cannot count on the Syrian government to effectively restrain Kurdish expansion in northern Syria. Either way, Turkey will have to deepen its involvement in Syria to manage the Kurdish threat directly.
Still, even a fledgling and inconclusive dialogue between Ankara and Damascus is extremely notable. Ankara has politically, militarily and ideologically pitted itself against the Syrian government, but it is still a pragmatic actor that will work with its adversaries to try to address urgent and common threats to its interests. With some common ground laid among Turkey, Syria and Iran in containing Kurdish autonomy, there is potential for a more substantive dialogue over a new power-sharing agreement for Syria.