The Russian president stressed that only Syrian people are to decide their own fate.
"I have repeatedly stated and I am ready to stress once again: we will never agree with the idea that a third party, whoever this party is, has the right to impose its will on another country. This does not make any sense. This is a violation of international legal standards," Putin said.
Vladimir Putin also added that he discussed the Syrian crisis with John Kerry during his Moscow visit.
"As soon as we notice the political process has begun, and the Syrian government decides it is time to stop the airstrikes, [we are going to stop]. We are not going to be more Syrians than Syrians themselves. We don't need this, do we? The sooner it [the process] starts the better," Putin said.
"We shall continue launching airstrikes and supporting the offensive of the Syrian army as long as the Syrian army carries out these operations," Putin said during his annual press conference.
Putin added that the Russian forces operating in Syria could be withdrawn in two days.
Russian President Vladimir Putin is holding a major end-of-the-year press conference, addressing the nation's economic concerns and issues on the international agenda.
Syria has been mired in civil war since 2011, with the army loyal to Assad fighting several opposition factions and militant groups, including the al-Nusra Front and Islamic State, outlawed in Russia and many other countries.