BEIRUT – Syrian troops backed by warplanes battled rebels for control of a key highway in Damascus on Saturday, a day after opposition forces cut the strategic artery as part of what they say are efforts to lay the groundwork for an eventual assault on the heavily defended capital.

Rebels have been on the offensive in Damascus since launching a series of attacks on government positions Wednesday. They brought their fight to within a mile of the heart of the capital Friday, seizing army checkpoints and cutting a key highway as they pressed their campaign for the city, the seat of President Bashar Assad’s power.

Additional Photos

Free Syrian Army fighters sit behind their anti-aircraft weapon in Aleppo, Syria, on Friday, as rebels brought their fight within a mile of the heart of Damascus. The Associated Press

The fighting is the heaviest to hit Damascus since July, when a first rebel assault managed to capture several neighborhoods before a punishing government counteroffensive. After that rebel foray, the regime quickly reasserted its control over the city, which has spared Damascus much of the violence and destruction that the civil war has wrought on other major urban centers.

Both the rebels and the government consider the fight for Damascus the most likely endgame in a civil war that has already killed more than 60,000 people. The city is heavily fortified and dotted with armed checkpoints, and activists say it is surrounded with three of the most loyal divisions of the army, including the Republican Guard and the 4th Division, commanded by Assad’s brother Maher.

The latest Damascus offensive did not appear to be coordinated with rebels on other sides of the capital, and it was unclear whether the opposition fighters would be able to hold their ground.

Activists said the fighting Saturday focused on a main highway that leads to northern Syria, a key road the regime uses to move troops and supplies. Rebels cut the road Friday, and still controlled parts of it Saturday despite government airstrikes and shelling to try to roll them back, said Damascus-based activist Maath al-Shami.

Activists say the fighting is only the beginning of a long battle for the capital.

“The attack was planned for more than 20 days and those responsible for it are army defectors,” al-Shami said. “This is one of the stages to enter the capital. …. Storming Damascus is not easy.”

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