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".
Sending foreign troops into Syria will lead to a "a full-fledged, long war", Russian Prime Minister Dmitry Medvedev has warned in an interview.
He spoke out after John Kerry, the US Secretary of State, said that more foreign troops could enter the conflict if attempts to reach a diplomatic solution fail.
The US has ruled out sending in ground troops - but Saudi Arabia this month offered to send ground forces to fight Islamic State.
Mr Medvedev hit back at Mr Kerry today in an interview with Euronews TV station, saying he should have held back his “futile words".
Major powers agreed on Friday to pause combat operations which have left at least 125,000 dead in the war-torn country.
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.