Flush from his country's triumph brokering a deal with ally Syria to avoid a U.S. attack, Russian President Vladimir Putin repeated that he believes Syrian rebels — not the Assad regime — were responsible for last month's chemical attack.

"We have every reason to believe that it was a provocation, a sly and ingenious one," he said of the Aug. 21 attack that killed more than 1,000 people, including children.

Its perpetrators relied on "primitive" technology, using old Soviet-made ammunition no longer in the Syrian army's inventory, Putin told a conference of Russia experts and media in Valdai, Russia.

A UN report released Monday confirmed that chemical weapons were used in the attack, but didn't assign any blame.

SYRIA-CRISIS/RUSSIA

Russian President Vladimir Putin, speaking at a conference of Russia experts and media in the town of Valdai on Thursday, said he couldn't be 100 per cent certain that a plan for the destruction of Syrian chemical weapons would be carried out successfully, but he saw reason to hope it would. (REUTERS)

Putin appeared confident in Syrian President Bashar al-Assad's commitment to surrender its chemical weapons and avoid a punitive U.S. military strike.

"If we find the answer to the question of who did it, no matter how difficult it would be — who committed this crime — [then] there will the next step," Reuters quoted Putin as saying. "Then we all together, with other colleagues in the [UN] Security Council should determine the level of responsibility."

Regarding the roundup of chemical weapons, he added: "I can't be 100 per cent sure that we will bring it to the end, but what we have seen in the past few days has given us confidence that it will be accomplished."

He insisted that Russia strongly opposed a U.S. attack on Syria because it would violate basic principles of international law and undermine the UN role, not because it was trying to keep Assad in power.

"We don't have some exclusive interests in Syria which we would seek to protect by defending the current government," Putin said.

"We are striving to preserve the principles of international law."

He said that during his discussions with Western leaders, they have failed to answer his question about what the West would do if al-Qaeda-linked militants finally unseat Assad and come to power in Syria.

"What sense does it make to launch a strike if you don't know how it will end?" Putin said.

The U.S. initially blamed the Syrian government for the chemical attack in the Damascus suburbs and, citing intelligence reports, said sarin gas was used. The U.S. said 1,429 people died, including 426 children.

With files from The Associated Press, Reuters