Negotiators are zeroing in on a potential deal to resolve one of the most explosive questions looming over Syria’s future: the fate of Kurdish forces that the US considers key allies against ISIS, but neighboring Turkey regards as a national security threat.Diplomatic and military negotiators from the United States, Turkey, Syria and the Kurdish-led Syrian Democratic Forces (SDF) are showing more flexibility and patience than their public statements suggest, a dozen sources told Reuters, including five directly involved in the intensive web of discussions in recent weeks.For all the latest headlines, follow our Google News channel online or via the app.This could set the stage for an accord in the coming months that would see some Kurdish fighters leave Syria’s restive northeast and others brought under the authority of the new defense ministry, six of the sources said.However, many thorny issues need to be resolved, they said.These include how to integrate the SDF alliance’s