(AFP) - Syrian government forces advanced on Sunday south of Aleppo city, a military source and state media said, as they pushed to once again encircle rebel neighborhoods and reimpose a siege. "The Syrian army, supported by allied forces, has total control of the armaments academy and expanded the territory it controls in the military academies zone," state news agency SANA said. An AFP correspondent in the rebel-held east of Aleppo city reported heavy aerial bombardment on the combat zone in the south of the city, where three military schools are located. Government forces have already recaptured the air force academy and rebels "are now besieged in the artillery academy," a military source said. If they recapture the school, government forces could then "easily take Ramussa, a suburb south of Aleppo, and reimpose a siege of the rebel districts," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights monitor. Once Syria's economic powerhouse, Aleppo city has been ravaged by the war that began with protests against President Bashar al-Assad in March 2011. It has been roughly divided between regime control in the west and rebel control in the east since mid-2012. In mid-July, advancing regime forces encircled the rebel-held east, placing the opposition districts under a siege that provoked international concern. But on August 6, opposition forces seized Ramussa and reopened a route into the rebel-held portions of the city. The reports come after the US said Sunday it had not yet struck a hoped-for deal with Russia on stemming the violence in Syria's brutal civil war, blaming Moscow for backtracking on issues it thought were settled. President Barack Obama said earlier that the two sides were "working around the clock" on the sidelines of a summit in China, but that it was "a very complicated piece of business." The State Department said a deal was close and could be announced by Secretary of State John Kerry and his Russian counterpart Sergei Lavrov, but hours later admitted defeat for now. "Russians walked back on some of the areas we thought we were agreed on, so we are going back to capitals to consult," a senior State Department official said. Kerry and Lavrov will meet again on Monday in Hangzhou, where G20 leaders are gathered, he added. Moscow and Washington support opposite sides in the Syrian conflict, which erupted in March 2011 after President Bashar al-Assad unleashed a brutal crackdown against a pro-democracy revolt. Successive rounds of international negotiations have failed to end a five-year conflict that has left more than 290,000 people dead and forced millions to flee, a key contributor to migrant flows into Europe. Russia is one of Assad's most important international backers while the US supports Syria's main opposition alliance and some rebels, with other countries and forces also involved. "Trying to corral all of those different forces into a coherent structure for negotiations is difficult," Obama said Sunday . "But our conversations with the Russians are key."
