Speaking at a Russian security council meeting, he said those who wanted to volunteer to fight with Russia-backed forces should be allowed to.
Russian Defence Minister Sergei Shoigu said there were 16,000 volunteers in the Middle East ready to fight alongside Russia-backed forces.
US officials said these could include Syrians skilled in urban combat.
Moscow is a long-standing ally of Syria and Mr Putin has been a key backer of Syrian President Bashar al-Assad in the country's civil war.
