For decades, the Assad family has settled loyal military families, many from its minority Alawite sect, in the western outskirts of Damascus, where the presidential palace sits on a plateau overlooking the city. The current fighting suggested that the government was trying to insulate those areas, along with the city center and airport, from the semicircle of urban sprawl curving from northeast to southwest, where rebels have strengthened their position in recent days, overrunning a string of small bases.

Analysts say that Mr. Assad, knowing that losing Damascus could be a decisive blow, has been conserving his best and most loyal troops and much of his artillery for a battle there.

“We’re not yet at a point where the regime is in total panic mode and can no longer make rational — however nasty — decisions about military strategy,” Mr. Hokayem said. “He has to decide which cities around Damascus to destroy and which cities to keep in hand.”

When Damascus was threatened in July, the government pulled forces from parts of northern and southern Syria — allowing rebels to consolidate gains in the north — and there were reports that something similar was happening now. An activist in Damascus said Saturday that elements of the army’s feared Fourth Division, led by Maher al-Assad, the president’s brother, were at the Aqraba military airport near the Damascus airport. There were unconfirmed reports that other top divisions and special forces were headed for the city, said Joseph Holliday, an analyst at the Institute for the Study of War, in Washington.

“When the rebels score victories in Damascus, it forces the regime to contract more quickly” in the areas that it contests elsewhere, he said.