But Putin said the erosion of Assad's regime might extend the war, not end it.
"We are worried about another thing: What happens next," he said. "We don't want to see the opposition come to power and start fighting the Government ... so that it goes on forever."
He said Russia does not seek "to keep Assad and his regime in power at any cost", but to foster an agreement among Syrians that "will ensure their safety and their participation in governing the country".
World powers have tried numerous times to push for a political solution in Syria, but neither side has shown any interest in negotiations, both thinking they can win militarily.
The Russian comments came as rebels seeking to drive Assad from power are making gains throughout the country, storming military bases in the north and expanding their control in a string of towns near the capital, Damascus, Assad's seat of power.
While few expect the 21-month conflict to end soon, analysts say the balance appears to be slowly tipping in favour of the rebels.
The Government says the rebels are foreign-backed terrorists who seek to destroy the country. While it does not report on the conflict's death toll, anti-regime activists say more than 40,000 people have been killed.
A new UN human rights report said the civil war is increasingly a sectarian conflict between rebels from the country's Sunni Muslim majority and government forces largely supported by the country's religious and ethnic minorities.
The report was released by an independent UN commission charged with investigating abuses during the war. It said most of the conflict's victims were civilians and that many were killed by government shell and bomb attacks that appeared "disproportionate" and did not discriminate between fighters and civilians.
It faulted opposition fighters for not differentiating themselves from the civilian population and for executing prisoners.
- AP