WASHINGTON (AP) — The Obama administration’s promise to limit U.S. military engagement against Islamic State militants makes it difficult to accept Turkey’s terms for joining the fight in neighboring Syria.

Turkey and other American allies want the U.S. to create a no-fly zone inside Syrian territory. Yet doing that would mean embracing one of two options President Barack Obama long has resisted: cooperating with Syrian President Bashar Assad’s government or taking out its air defenses, an action tantamount to war.