THE UNITED STATES has pretty much exhausted direct economic sanctions, and NATO has preemptively ruled out a Libya-type military intervention. So for now, at least, the besieged people of Syria must look for relief from their neighbors. It is a shaky bet: Iraq has inclined toward the dictatorship of Bashar al-Assad, while the rest of the Arab League and Turkey have been slow to condemn its slaughter of civilians and even slower to take action. Now, however, there is a prospect that both Ankara and the Arabs will turn up the pressure on Mr. Assad. That creates a good opportunity for the back-seat leadership the Obama administration is fond of.

The Arab League announced Wednesday that Syria had accepted its proposal for ending the violence, which it said was aimed at preventing foreign intervention. Led by Qatar, the league put forward what appeared to be a robust set of demands — that the regime withdraw tanks and troops from the streets, free political prisoners, accept Arab observers and foreign journalists, and open negotiations with the opposition within two weeks. Were Damascus to fulfill these terms, it would spell the end of the Assad dictatorship — which is why they won’t be met. Mr. Assad has made a habit of promising radical steps to outsiders, ranging from Turkey’s envoys to Sen. John F. Kerry (D-Mass.) and other interlocutors in Washington. He has never delivered.

The next question, consequently, is what the Arab League will do when the killing continues. Suspending Syria’s membership is one obvious step. But the Obama administration and other Western governments should be quietly lobbying for far stronger action. Arab support for a U.N. Security Council resolution ordering a halt to the violence and threatening sanctions could break the resistance of Russia and China, which vetoed an earlier measure. The Arabs could also endorse international efforts to protect the Syrian population, as they did in the case of Libya.

If there is to be such protection, a pivotal player will be Turkey, which is reportedly already sheltering leaders of a rebel Syrian army in a refu­gee camp. Prime Minister Recep Tayyip Erdogan is furious with Mr. Assad, whom he had cultivated for years, for ignoring Turkey’s pleas to stop the violence, and his government has said that it is preparing to impose sanctions. Even “targeted” Turkish economic sanctions, as promised by its foreign minister, could help peel away the support that the regime still has from the ­Syrian business community.

Turkey could also formally guarantee protection along the border for civilians fleeing the regime as well as for defecting soldiers. And if that is not sufficient, it could carve out a buffer zone inside Syria, protected by a no-fly zone. As a NATO member, Turkey should enjoy the alliance’s backing if Syria responds belligerently.

President Obama reportedly enjoys a good relationship with Mr. Erdogan and has already spoken to him at length about Syria. Now would be a good time to press for a robust Turkish response to Mr. Assad’s crimes — and offer assurance that the United States will support a Turkish effort to protect Syrian civilians.