Damascus: Moscow pressed its military buildup at a new airbase in Syria on Saturday, as Washington admitted that rebels it trained handed ammunition and equipment to al Qaeda in a fresh setback for US policy.
A decades-long backer of the Damascus regime, Moscow has remained a steadfast supporter of President Bashar al-Assad throughout four and a half years of war that have left more than 240,000 people dead.
Its recent deployment of its own troops and warplanes to Syria, combined with new arms deliveries to Assad`s armed forces, appear to have prompted a significant shift in international efforts to end the conflict.
On Monday, Russian President Vladimir Putin will meet his US counterpart President Barack Obama on the sidelines of the UN General Assembly meeting in New York.
Saturday was the 15th straight day that Russian transport aircraft had flown in troops and equipment to the Hmeimim base in Latakia province on the Mediterranean coast, a military source told AFP on condition of anonymity.
"For the past two weeks and again today a Russian cargo plane has landed every morning at Hmeimim," the source said, adding that they all had fighter escorts.
At least some of the cargo was then unloaded and transported out of the airport, the source said.
US satellites have recorded increased activity by Russian forces at the base inside the Bassel al-Assad civil and military airport.
On Wednesday, the Syrian army used Russian-delivered drones for the first time, a security source in Damascus said.
Washington and NATO say that recent spotting of helicopters, bombers, ground attack aircraft, tanks and soldiers prove that Russia is building an airbase in Latakia, the Assad regime`s coastal heartland.
Russian military aircraft have conducted reconnaissance flights over Syria but not yet launched any strikes, the Pentagon said.
One senior Syrian official called Russia`s military involvement a "turning point".
Hassan Nasrallah, the leader of Lebanese Shi`ite militant group Hezbollah, which has fought alongside Assad`s forces, said new Russian military support would "affect the evolution of the ongoing battle in Syria."
The US has said it "could find areas of cooperation" with Russia if Moscow were to join the fight against the Islamic State jihadist group. Moscow`s intervention comes with Washington`s own policy for fighting IS in Syria in increasing disarray.
The United States has a $500-million programme to train and equip vetted moderates recruited from among the rebels fighting Assad`s forces but it has faced repeated setbacks.
In a shock admission on Friday, the Pentagon said that a group of US-trained rebels had handed over ammunition and equipment to Al-Qaeda`s Syria affiliate, the Al-Nusra Front, purportedly in exchange for safe passage.
"Unfortunately, we learned late today that the NSF (New Syrian Forces) unit now says it did in fact provide six pickup trucks and a portion of their ammunition to a suspected Al-Nusra Front (group)," Pentagon spokesman Captain Jeff Davis said.
The unit, which included about 70 rebels, were trained in Turkey and sent back to Syria last weekend.
Colonel Patrick Ryder, a spokesman for Central Command (CENTCOM), which is overseeing the campaign against IS, said the fighters had handed over the gear in exchange for safe passage through the Al-Nusra operating area.
He said the pickup vehicles and ammunition represented about 25 percent of the equipment issued to the group by the US-led coalition.
"If accurate, the report of NSF members providing equipment to Al-Nusra Front is very concerning and a violation of Syria train-and-equip programme guidelines," Ryder said.
It was just the latest blow for the troubled programme. The first 54 graduates were attacked by Al-Nusra in July, and the Pentagon says it is not sure what happened to them.
Last week, before the insertion of the new fighters, the US general overseeing efforts against IS drew disbelief from senior lawmakers when he told them only "four or five" US-trained rebels were on the ground fighting in Syria.