Russian Prime Minister Dmitry Medvedev has warned that sending more foreign ground troops into Syria will result in "a full-fledged, long war".
He hit back at the US Secretary of State John Kerry, who has suggested more countries could enter the conflict if diplomatic efforts fail to reach a solution.
The Russian PM has also said ongoing tensions between Russia and the West have plunged the world into "a new period of Cold War".
Russia has been accused by its western allies of jeopardising peace in Syria by bombing the wrong targets as a recently agreed ceasefires hangs in the balance.
But Russian Prime Minister Dmitry Medvedev has spoken during a security conference in Munich to deny that Russian forces are bombing civilians.
ITV Political Correspondent Paul Brand reports:
Syrian President Bashar al-Assad has vowed to regain control of the entire country but warned it could "take a long time".
Marathon talks agree a partial ceasefire but fail to secure an end to Russian bombing, while rapid humanitarian aid won't reach all Syrians.