BEIRUT, Lebanon — Turkey, Saudi Arabia and Qatar, three of the Middle East’s major Sunni powers, once equated their standings in the region with the outcome of the war in Syria. Since the uprising broke out in 2011, they have been stalwart — if often divided — supporters of the rebels in their fight against the government of President Bashar al-Assad.

In the last several months, it became clear they were on the losing side. Recent events, including the fall of eastern Aleppo this month, are compelling these countries to adjust their strategies. A cease-fire agreement brokered by Russia and Turkey and announced on Thursday has only made it clearer that in the Middle East, force drives diplomacy.

The mainstream rebel groups that Turkey, Saudi Arabia and Qatar have backed since 2011 are now morphing into a rural insurgency. This will mean they are less of a threat to the Assad government, but more vulnerable to being defeated by jihadist groups — or lured into joining them. Supporting these rebels will soon become even more difficult, especially if President-elect Donald J. Trump follows through on campaign pledges to end American aid to rebel groups and to work more closely with Russia to fight jihadists in Syria.

For Turkey, Saudi Arabia and Qatar, this situation raises major moral and political questions: If military victory is no longer feasible, why should they continue to support rebels at the cost of more Syrian lives? Can they and their rebel proxies carve out zones of influence that will allow them to shape Syria’s future? Should the rebellion’s sponsors cut their losses and force the rebels to capitulate in exchange for whatever favor Russia is able to offer, such as facilitating Turkish policy in Central Asia or helping Saudi Arabia extricate itself from Yemen? Or should they let the rebellion slowly die? Wouldn’t doing so only encourage Iranian aggressiveness and prove right the jihadist groups that say Arab countries are impotent and treacherous?