UNITED NATIONS — For four years, the United Nations Security Council has been unable to agree on what to say — let alone what to do — to stop the civil war in Syria.

On Monday, the Council managed to adopt a modest statement, nudging the Syrian government and its opponents to discuss a “political transition,” while sidestepping the thorny question of what to do about the man at the center of the war: Syria’s president, Bashar al-Assad.

The statement came a day after Mr. Assad’s forces bombed a rebel-held town just outside the capital of Damascus, killing about 100 people. It was one of the deadliest single air attacks in the war, which has so far resulted in 250,000 deaths and forced half the population to flee their homes.

The top United Nations official for humanitarian affairs, Stephen O’Brien, at the end of a three-day visit to Syria, on Monday called the airstrikes “appalling.” The United Nations’ envoy to Syria, Staffan de Mistura, said the airstrikes were “unacceptable in any circumstances.”