Deputy foreign minister Mikhail Bogdanov said earlier this week the Syrian regime is losing "more and more control" and military defeat for Mr Assad's regime could no longer be ruled out.
A spokesman for Russia's foreign ministry says Mr Bogdanov's comments do not reflect official policy.
"We have never changed our position [on Syria] and we never will," foreign ministry spokesman Alexander Lukashevich said.
Mr Bogdanov's comments, which were reported by several Russian news agencies, appeared to mark a major policy shift by Russia, which has repeatedly used its veto powers in the United Nations Security Council to shield its ally.
The United States welcomed the Mr Bogdanov's comments, saying it appeared Russia was "finally waking up to the reality" to which Mr Lukashevich retorted "we were never sleeping to begin with".
The announcement comes even as US officials said they would deploy two Patriot missile batteries and 400 troops to Turkey to help defend against potential threats from Syria.
The move coincides with rising fears the Syrian regime may resort to using chemical weapons against rebel forces and after Mr Assad's army fired Scud missiles against rebels.
US and European leaders have warned Mr Assad's regime not to use its arsenal of chemical arms, saying it is a "red line" that would trigger international military action.
Germany and the Netherlands also have agreed to provide advanced "hit-to-kill" Patriot weapons, which are designed to knock out cruise and ballistic missiles as well as aircraft.
Meanwhile, the UN says it remains committed to maintaining aid operations and ensuring adequate relief supplies are stocked in neighbouring countries.
"We are looking at making sure that we have adequate stockpiles in neighbouring countries," UN humanitarian chief Valerie Amos said.
"We all have staff who are still on the ground - of course we will continue to look at the safety and security of our staff, but our commitment is to keep our operations going."
Earlier this month, the UN withdrew a quarter of its 100-strong team of foreign aid workers from Syria as fighting intensified between government forces and rebels closing in on Damascus.
The UN's World Food Programme is distributing food rations to about 1.5 million people inside Syria, including 1.1 million who have been forced to flee their homes during the 20-month conflict, WFP executive director Ertharin Cousin said.
"We are continuing to move our convoys out of Damascus," she told reporters.
"We are challenged every day by shrinking humanitarian space in different parts of the country. Yet we continue to distribute food to persons in need."