Reuters, Washington, 28 July 2015
The United States and Turkey have not yet agreed which Syrian opposition fighters they will support in a joint effort to help clear Islamic State from an area along the Turkish border, officials said on Tuesday, underscoring uncertainty surrounding the campaign plan.
Washington and Ankara this week announced their intention to provide air cover for Syrian rebels and jointly sweep Islamic State fighters from a strip of land along the border, with U.S. warplanes using bases in Turkey for strikes.
But planning appears to be just getting under way and resolving crucial details, like which opposition groups will be supported on the ground, could stoke longstanding tensions between the United States and Turkey about Syria strategy.
Also still to be resolved in talks with Turkey, officials say, are how deep into Syria the area might extend and how quickly U.S. warplanes will begin flying combat missions from Turkish bases.

TURKEY AND BORDER ZONE
Robert Ford, a former U.S. ambassador to Syria, said Turkey would likely have the greater say on security arrangements in the zone near its border, partly because of its proximity.
Ford, now at the Middle East Institute, said Washington will not work with Nusra Front, an al Qaeda-linked group that is part of a coalition that he said has received Turkish backing. But as for less hardline Islamist groups, “I guess the administration can live with that,” he said.