"Unfortunately we have to pay for the mistakes of others. We would be happy to spend this funding on other means….but we have to carry out the operation in Syria," Kosachev said, speaking at a meeting with Romanian Ambassador Vasile Soare.
The Russian official said that a US-led operation in Syria did not achieve results in its fight against Islamic State (ISIL) militants in Syria.
A US-led international coalition has been launching airstrikes against the ISIL in Syria since 2014 without the approval of the UN Security Council or the Damascus authority.
Syria has been in a state of civil war since 2011, with troops loyal to Assad fighting on multiple fronts against opposition factions and extremist groups, including Islamic State (ISIL).
Since the beginning of the Syrian civil war, the United States and its allies have provided military to opposition factions they consider to be "moderate," and have called for Assad to resign.
Russia considers Assad the legitimate authority in the country, stating that the Syrian people must choose their leader without outside intervention.