Forces loyal to embattled Syrian President Bashar Assad are reported tightening a cordon around the northern city of Aleppo, once the country's commercial heart, in a major offensive against rebels who hold 60 percent of the city.

The regime, dominated by the minority Alawite sect, is massing tanks and artillery around the ancient city that was once part of the famed Silk Road to China, for the coming showdown military analysts say could determine the course of the civil war, now in its third year.

Assad's troops were greatly buoyed by their capture of the strategic town of Qusair in central Syria's Homs province June 5 after a three-week battle.

The town, which controls supply routes from neighboring Lebanon, had been held by rebel forces for more than a year, cutting off Damascus from the Alawite heartland in the northwest.

The fall of Qusair after fierce fighting opened the way for the regime to push into central Syria in a drive to recapture territory held by the rebels, including Homs, the provincial capital, and Aleppo, the big prize.

The regime needs to take control of Aleppo to undercut the rebellion that erupted March 15, 2011, and to reassert dominance of Syria's main population centers.

A rebel defeat in Aleppo would mean a critical and possibly terminal setback for those seeking to end Assad's rule.

U.S. President Barack Obama's decision Thursday to arm rebel forces -- although it's not clear whether arms would include urgently needed anti-aircraft and anti-tank missiles -- could make a critical difference if the flow starts quickly.

The U.S. move overturned two years of reluctance by the West to get directly involved in the Syrian fighting, which threatens to spill over into neighboring states like Lebanon, Jordan, Iraq and Turkey.

Indeed, it was the regime's conquest of Qusair, largely due to fighters from Lebanon's Hezbollah who spearheaded the assault, that convinced Obama U.S. aid should be increased from medicine and supplies to include arms.

Much will depend on how swiftly the Americans can start the arms flowing to the rebels through Jordan and Turkey.

Rebels report Syrian warplanes attacked their positions around the contested Kweiras airbase near Aleppo Tuesday amid heavy ground skirmishes.

The regime's command of the air is a major problem for the rebels, and unless they get surface-to-air missiles they will face serious problems in the looming battle for Aleppo.

The air force has carried out a series of aerial resupply operations in the region in the last two months that rebels have been powerless to prevent.

But it's not all clear sailing for the regime forces either.

They face major obstacles in the push on Aleppo from well-entrenched rebel blocking positions, which are being supplied with weapons through Turkey, Syria's northern neighbor, funded by Saudi Arabia and Qatar.

Loyalist forces have seized several villages in Homs province in recent days to consolidate their Qusair victory.

"Troop movements and bombardment patterns suggest the regime will likely stage attacks on rebels in Homs city proper and around the towns of Rastan and Talbiseh along the M5 highway, which leads from the Jordanian border in the south, through Damascus and all the way north to Aleppo," the U.S.-based global security consulting firm Stratfor says.

Analysts say the regime's assault on Aleppo may be deferred until there's a significant loyalist push from the south as well.

"For all the regime's announcements of an imminent victory in Aleppo, it is important to remember the very significant obstacles," Statfor stressed. "Many of these are in fact the same that prevented the regime from ousting the rebels from the city in the summer of 2012."

The rebels are dug in along much of the M5, which the regime would need to control to supply a major mechanized force.

Activists say rebels have already sent blocking forces to key supply routes in anticipation of a regime push northward from Hama province.

The Iranian-backed Hezbollah will likely play a key role in the Aleppo offensive as a strike force, as it did in the battle of Qusair.

The Shiite movement, which has fought the Israelis for three decades, has proven to be a staunch ally of Assad's Alawites, an offshoot of Shiite Islam.