US President Barack Obama insisted Tuesday that Russia had made a strategic error in propping up Syrian ruler Bashar al-Assad, but said the conflict was not about him and Vladimir Putin, AFP reports.

Predicting a "quagmire" that drains Russia's assets, Obama said "this is not a contest between me and Putin."

"The real question we should be asking is what is it that Russia thinks it gains if it gets a country that's been completely destroyed as an ally, that it now has to perpetually spend billions of dollars to prop up?" Obama said. "Putin may think that he's prepared to invest in a permanent occupation of Syria with Russian military. That's going to be pretty costly."

"About three-quarters of the country is still under control of folks other than Assad. That's not stopping anytime soon."