President Vladimir Putin has said Russia had no plans "right now" to put combat troops in Syria, but would continue backing the Syrian government.
The Russian leader also sharply criticized U.S. military support for Syrian rebels, describing it as not only illegal but counterproductive.
Putin was speaking in an interview broadcast on September 27 on the eve of his meeting with President Barack Obama.
Putin and Obama are scheduled to meet on the sidelines of the UN General Assembly, after both address the annual gathering of world leaders.
Besides the crisis in Syria, U.S. officials say Obama and Putin will discuss the simmering conflict in eastern Ukraine, where the Kremlin is accused of backing pro-Russian separatists.
Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry met on September 27 to prepare the ground for the presidents' meeting.
A Russian military buildup in Syria, a longtime ally, has raised concerns in Washington. Putin and other officials have said only that Russia was providing weapons and training to Syrian President Bashar al Assad's army to help it combat the Islamic State extremist group.
Asked if Russia could send troops to join the fight, Putin previously said "we are looking at various options."
"Russia will not participate in any troop operations in the territory of Syria or in any other states. Well, at least we don't plan on it right now," Putin said in the interview on CBS' "60 Minutes."
Putin noted the Pentagon's recent admission that an effort to train more than 5,000 Syrian rebels had yielded only four or five fighters after about 50 others were captured, wounded or fled in their first encounter with extremist militants.
Putin defended Russia's military buildup in Syria and support for Assad, describing the Syrian government army as the only legitimate one in Syria and said the U.S. military support for "illegal structures" ran counter to international law and the UN charter.