President Barack Obama declared Monday that the United States does not want a new Cold War over the Ukraine conflict and is prepared to work with Russia and Iran on the Syrian crisis.
"The United States is prepared to work with any nation, including Russia and Iran, to resolve the conflict," Obama said of Syria, addressing the United Nations General Assembly.
Russia's President Vladimir Putin was due to address the assembly later and has urged world powers to back Syria's President Bashar al-Assad in his battle against the Islamic State terror group.
Obama argued it would be wrong to support a "tyrant" like Assad, but that Washington was ready to work with anyone ready to take on the jihadist threat, even Moscow and traditional US foe Tehran.
Russia has stepped up its military involvement in Syria in recent weeks, with U.S. officials accusing Moscow of sending combat aircraft, tanks and other equipment to help the Syrian army.
The United States was so concerned about reports of Russia’s increased presence in Syria that Secretary of State John Kerry phoned his Russian counterpart Sergei Lavrov a total of three times in ten days to discuss the situation.
Obama spoke just hours after Putin reportedly stated that American support for Syrian rebels is "illegal and ineffective."
"No Cold War" over Ukraine
Obama insisted that the sanctions Western powers imposed on Moscow in the wake of Russia's intervention in Ukraine were meant to protect Kiev's sovereignty - not trigger conflict with Moscow.
"We cannot stand by when the sovereignty and territorial integrity of a nation is flagrantly violated," he said.
"If that happens without consequence in Ukraine, it could happen to any nation gathered here today."
"That's the basis of the sanctions that the United States and our partners impose on Russia. It is not a desire to return to a Cold War," he said.
AFP contributed to this report.