Russia has called an urgent UNSC meeting to demand an explanation of the US for the bombing that killed at least 62 Syrian soldiers
The US Ambassador to the United Nations Samantha Power expressed regret on Saturday over the US-led coalition strike on a Syrian army post, but dismissed Russia's call for an emergency Security Council meeting as a "stunt."
Russia called the urgent meeting to demand an explanation from the United States after the bombing killed at least 62 soldiers in eastern Syria, near the Islamic State group-controlled town of Deir Ezzor.
"We are investigating the incident," Power told journalists as the closed door meeting got under way.
"If we determine that we did indeed strike Syrian military personnel, that was not our intention. And we of course regret the loss of life," she added.
Power went on to describe Russia's request for the urgent meeting as a "stunt, replete with moralism and grandstanding," saying Moscow should instead demand a meeting with the Assad regime to press for peace.
In an exchange reminiscent of Cold War-era verbal jousting, Russian Ambassador Vitaly Churkin returned by accusing the United States of violating agreements that it would not target Syrian positions and said the action was a "bad omen" for a US-Russian deal on halting the fighting in Syria.
Washington and Moscow reached an agreement in September that calls for a ceasefire, the delivery of aid and the joint targeting of Islamist rebels in Syria.
The ceasefire went into effect on Monday, but convoys of aid have yet to reach civilians besieged by Syrian forces in the battleground city of Aleppo.
Asked if the air strike on the Syrian army would kill off the US-Russian deal, Churkin said "this is a very big question mark."
"I do hope that they will find a way to convince us and everybody else that they are serious about political settlement in Syria, serious about fighting terrorists," he said.
US secretary of state John Kerry and Russian foreign minister Sergei Lavrov are due on Wednesday to attend a special Security Council meeting on Syria, held on the sidelines of the UN General Assembly meeting.