The U.S. and its allies raised the possibility of setting up a safe zone for refugees along the Syrian-Turkish border—a proposal that the government in Ankara has been pushing heavily.

But U.S. defense and White House officials just as quickly cast doubt on the idea. Though Secretary of State John Kerry on Wednesday said the creation of a buffer zone is “worth looking at very closely,” Rear Adm. John Kirby, the Defense Department press secretary, said a buffer zone “is not now on the table as a military option that we are considering.” White House press secretary Josh Earnest said a buffer zone is “not something that is under consideration right now.”

French President François Hollande backed the idea of a buffer zone in a phone call with his Turkish counterpart, the French presidency said. U.K. Foreign Secretary Philip Hammond said it was a possible option.

The three-week-long Islamic State siege of Kobani, a Kurdish-majority town in northern Syria near the Turkish border, has put pressure on the U.S. and its allies to act. It has also created a new refugee crisis in Turkey and sparked protests by Kurds in that country that could escalate. In two days of clashes and demonstrations, 21 people have died, Turkish media reported.

Islamic State extremists massed more forces around Kobani on Wednesday despite a fresh spate of American-led airstrikes, Kurdish fighters and Turkish officials said.