US President Barack Obama must not wait until his re-election bid is resolved to take action to stop the slaughter of thousands in Syria, the head of the main Syrian opposition group said Sunday.

“We would like to say to President Obama that waiting for election day to make the right decision on Syria is unacceptable for Syrians,” Abdel Basset Sayda, president of the Syria National Council, told CNN.

“We cannot understand that a superpower ignores the killing of tens of thousands of Syrian civilians because of an election campaign that a president may win or lose.”

Obama, waging a tough domestic battle ahead of the November 6 election, has demanded Syrian President Bashar Al Assad stand down and offered logistical support to the opposition, but his administration has ruled out using force.

International efforts to squeeze Assad by isolating his regime and seeking sanctions against his inner circle have been frustrated by Russian and Chinese opposition at the UN Security Council.

Speaking to CNN’s Fareed Zakaria from Istanbul, Turkey, after the alleged massacre of more than 150 people in one of the bloodiest episodes of Syria’s 16-month uprising, Sayda said it was imperative world leaders took action now.

“If it continues like this, it will lead to the explosion of everything in the Middle East. It will threaten the security and the peace of the region and even the world. For this reason, everybody must move before it is too late,” he said, speaking through a translator.

Sayda’s latest meetings with the Russians made no progress in ending their political and military support for the Assad regime.

“During the negotiations which lasted for more than three hours, we found that the Russian point of view is still the same,” he said.

“We told them that you’re supporting this regime by using veto power in the Security Council.

“We told them that the Syrians are being killed by Russian weapons, especially by artillery, tanks, cannon, rocket launchers, and helicopters.

“Their answer is that they had stopped shipments of arms,” he said.

“We know that Russia is the superpower who has its own interests. We respect all this, and we understand it. But we cannot accept that these interests come at the expense of the blood of Syrians.”