BEIRUT, Lebanon — The failure of an Arab League mission to stanch violence in Syria, an international community with little leverage and a government as defiant as its opposition is in disarray have left Syria descending into a protracted, chaotic and perhaps unnegotiable conflict.

The opposition speaks less of prospects for the fall of President Bashar al-Assad and more about a civil war that some argue has already begun, with the government losing control over some regions and its authority ebbing in the suburbs of the capital and parts of major cities like Homs and Hama. Even the capital, Damascus, which had remained calm for months, has been carved up with checkpoints and its residents have been frightened by the sounds of gunfire.

The deepening stalemate underlines the extent to which events are slipping out of control. In a town about a half-hour drive from Damascus, the police station was recently burned down and in retaliation electricity and water were cut off, diplomats say. For a time, residents drew water in buckets from a well. Some people are too afraid to drive major highways at night.

In Homs, a city that a Lebanese politician called “the Stalingrad of the Syrian revolution,” reports have grown of sectarian cleansing of once-mixed neighborhoods, where some roads have become borders too dangerous for taxis to cross. In a suggestion that reflected the sense of desperation, the emir of Qatar said in an interview with CBS, an excerpt of which was released Saturday, that Arab troops should intervene in Syria to “stop the killing.”