WASHINGTON — The retired Marine general in charge of mobilizing an international coalition against the group that calls itself the Islamic State (IS) says that the United States has not ruled out a no-fly zone or protected corridor in Syria to safeguard the thousands of fighters it intends to train to help defeat the militant group. 

“All those things are under consideration,” John Allen told an audience the evening of March 2 at the Atlantic Council, a Washington-based think tank.

Allen bristled when asked if the 5,000 moderate Syrians that the United States says it plans to train each year for the next three years in Turkey, Qatar and Saudi Arabia would face certain death once injected onto the battlefield. “We will protect them when the time comes,” Allen said.

Syrian opposition forces and Turkey have long urged the Obama administration to establish a protected zone in northern Syria along the Turkish border to reduce the number of refugees streaming out of the country and make it easier for the opposition to the regime of President Bashar al-Assad to govern a piece of liberated land. But the White House has so far resisted these appeals and since last summer has focused less on confronting Assad than on defeating IS forces that have seized a third of Syrian territory and Sunni Muslim areas in Iraq.