"I am speaking theoretically and hypothetically, but if we become convinced that (Syrian President Bashar) al-Assad is cheating, we can change our position," the Kremlin chief of staff Sergei Ivanov was quoted as saying by Russian news agencies.
He was speaking at a conference in Stockholm organised by the International Institute for Strategic Studies.
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Ivanov did not clarify his remarks, and reiterated Russia's opposition to intervention in the country wracked by civil war that has killed more than 110,000 in 30 months.
He added that he expects the locations of the Syrian chemical arsenal to be disclosed within a week, but cautioned that the army does not control the entire country.
"We still don't know where the chemical weapons are located geographically. I think this will become clear within a week," Ivanov said.
The US-Russian plan to dismantle the chemical arms stockpile has helped prevent US-led military action following a chemical attack last month that killed hundreds of people and which Washington blames on the regime.
Under the plan, Assad's regime had until Saturday to supply details of its arsenal.
On the eve of the disclosure deadline, the Organisation for Prohibition of Chemical Weapons said it "has received an initial disclosure from the Syrian government of its chemical weapons programme."
Russia has strongly opposed sanctions or strikes against Assad's regime and has said the sarin gas attack on August 21 was likely perpetrated by the rebels.
President Vladimir Putin on Thursday said that he "doesn't know" if Russia can convince Assad to destroy his chemical arsenal. "So far, everything looks as if Syria has completely agreed with our proposal," he said, adding that the regime's actions "inspire confidence."
Meanwhile, in an interview with Russian public television conducted Wednesday but broadcast Saturday, Ivanov addressed the discovery of Cyrillic writing on artillery shell fragments photographed by UN weapons inspectors in Syria.
"In effect, they found Cyrillic on a Soviet surface-to-surface missile made between 1950 and 1960," he said.
"At the time Soviet weapons were being shipped to dozens of countries," he said.
Such missiles "were found in particular in Libya, whose stocks were pillaged during the so-called democratic revolution," Ivanov said.
