The Pentagon on Monday played down the idea of creating a buffer zone along the Syria-Turkish border after a media report cited it as a possible concession to Turkey in return for the use of bases to launch air strikes against Islamic State militants in Syria.
The Wall Street Journal, citing unnamed U.S. and Turkish officials, reported that an agreement could include a safe zone along part of the Syrian border to protect refugees and certain opposition forces that would also "be off-limits" to aircraft from Syrian President Bashar al-Assad's government.
Ankara has long sought a no-fly, or safe, zone.
"We are in discussions with the Turks. Right now, we don't believe a buffer zone is the best way to relieve the humanitarian crisis there in northern Syria," Colonel Steve Warren, a Pentagon spokesman, told reporters.
"But they are close allies, partners and friends, and we are in discussions with them about the way forward."
According to the WSJ report, the agreement would move away from the idea of a larger, formal "no fly" zone that had been sought by Turkish officials, covering a wider swath of northern Syria.
A protected zone along the Turkish-Syrian border would help safeguard opposition fighters being trained in Syria and shield opposition supply lines, the report said.
Asked what might be better than a buffer zone to relieve the humanitarian crisis, Warren said: "Continuing for us to apply pressure on (Islamic State militants) is probably the most effective way to relieve that crisis."
Ankara's plans for establishing safe zones, with air defense as a key component, have received a cool reception from many NATO allies.
Military experts say it would necessitate either agreement from the Syrian government or taking out Damascus' advanced air defense systems.
Such a move would risk dragging Western powers further into Syria's three-year-old war, and anger President Bashar al-Assad's allies, Russia and Iran.
Complicating matters, Assad is using the U.S. air strikes as cover for his own air campaign against Syrian rebels, hitting the Islamic State stronghold of Raqqa in retaliation for the group's killing of Syrian soldiers.