"There is some indication that they (the Russians) have assured the regime that if we destroy something, they can replace it," General Martin Dempsey, chairman of the US military's Joint Chiefs of Staff told a Senate hearing on Tuesday.
Dempsey, however, added that it was not a reason in his view to hesitate to act Syria.
The top US military officer said that he had not been asked to change the momentum in the Syrian conflict, but instead develop options to degrade Syria's military capabilities.
"I have never been told to change the momentum. I have been told to degrade capability," Dempsey said.
On Tuesday, the US Congress held its first hearing about the White House’s plan for military intervention in Syria.
US President Barack Obama has called for a prompt vote from Congress authorizing the use of force in Syria.
The call for military action against Syria intensified after foreign-backed opposition forces accused the government of President Bashar al-Assad of launching a chemical attack on militant strongholds in the suburbs of Damascus on August 21.
Damascus has vehemently denied the accusations, saying the chemical attack was carried out by the militants themselves as a false-flag operation.
Syria says it will retaliate any attack on the country with full force.
BA/BA