Renewed calls from Russian President, Vladimir Putin to support Syrian President, Bashar al Assad were fully rejected by the US, saying they were "destabilising and counterproductive."
White House spokesman, Josh Earnest said that the US wants to see more "constructive engagement" from Russia with the US-led coalition battling ISIS.
"We would welcome Russia's participation in that effort," Earnest said.
The US-led coalition comprises 60 countries, and undertakes air strikes against ISIS in Syria and Iraq.
Earnest was reacting to Russian President, Vladimir Putin comments in Dushanbe, Tajikistan, at a summit of the Collective Security Treaty Organization, a post-Soviet military alliance, where he urged the international community to help Russia support Assad.
"We support the government in Syria in their resistance against terrorist aggression and continue to supply military-technical assistance," Putin said.
Russian troops have recently been deployed in Syria’s coastal governorate of Latakia, to provide supplies to the areas under the control of Assad’s regime.
Russia and Iran have been the main allies of the Assad regime throughout the civil war which started in March 2011.
More than 240,000 people have died in the conflict, many of whom are victims of the Assad regime, according to the Syrian Observatory for Human Rights (SOHR). Millions were displaced internally and internationally to neighbouring countries like Turkey - that hosts almost 2 million Syrians - as well as Lebanon, Jordan and Egypt.
War, hunger and desperation has pushed thousands of Syrian refugees into taking dangerous sea journeys to Europe, hundreds have died along the way and hundreds are still missing.
New anti-ISIS Russian-led coalition
Russia has been pushing to form a new international coalition to fight ISIS, which would include Assad, in what they call a “healthy opposition.”
However the US does not see the need for a new coalition when there’s already an existing one active in the region with battling the insurgency, State Department spokesman, John Kirby said.
"There's already an international coalition dedicated to that," Kirby said.
“While the US would welcome a constructive role by Russia, Assad cannot be a part of that coalition."
Earnest and Kirby reiterated that the US sees Assad as a president who "has lost legitimacy" to lead Syria and that a "political transition away from Assad" should occur.