Washington warned Russia that Syrian leader Bashar al-Assad has no role in the fight against the Islamic State after the Kremlin launched a new drive to rehabilitate the embattled Syrian leader.
Secretary of State John Kerry told his Russian counterpart Sergei Lavrov in a phone call late September 15 that the United States has not changed its position that the Syrian president must step aside so that other parties can reach a political settlement to end the country's four-year civil war.
Kerry's call came hours after Russian President Vladimir Putin asserted that Russia intends to keep supplying military support to Assad and invited the rest of the world to join Assad's government in a coalition to defeat IS.
At the same time, Russia's news media featured an interview with Assad calling for a rapprochement with the West and Syrian rebel groups so they can work together to defeat IS.
And Russia's envoy to the United Nations, Vitaly Churkin, asserted in an interview with CBS that, despite public statements to the contrary, the United States no longer wants Assad's government to fall.
"One of the very serious concerns of the American government now is that the Assad regime will fall and IS will take over Damascus, and the United States will be blamed for that," Churkin said.
Responding to the barrage of Kremlin moves promoting Assad, Kerry's office issued a statement late September 15 saying Kerry told Lavrov that "Russia's continued support for President Assad risks exacerbating and extending the conflict, and undermining our shared goal of fighting extremism."
Kerry "reaffirmed the U.S. commitment to fight ISIL with a coalition of more than 60 countries, of which Assad could never be a credible member," it said.
"The secretary stressed that there is no military solution to the overall conflict in Syria, which can only be resolved by a political transition away from Assad."
The United States only a few weeks ago had hoped to convince Russia, a long-standing ally of Damascus, to help persuade Assad to step down and permit a transitional government as part of a negotiated deal to end Syria's civil war.
But this month, Moscow has openly bulked up its forces and troops in Syria with the goal of propping up the government.
Moscow sees Assad's army as a bulwark against Islamist rebels, while Washington and its allies insist Damascus government itself is part of the problem. The West has been bombarding IS positions inside Syria, and supporting "moderate" rebel forces in the war against IS and the government there.
Russia showed September 15 that it is stepping up its support for Assad in other ways as well. In an extensive interview Assad granted to Russian government-backed news services, Assad made a personal appeal to the West and rebel forces fighting his army to join together to fight IS and other terrorist organizations operating out of Syria.
"I say that political forces, government, or illegal armed units who fought against the government should unite for the sake of the struggle against terrorism," he said.
Assad credited Tehran and Russia with supplying the arms and back-up resources the Syrian government has needed to persevere during the long civil war.
The White House joined Kerry in urging Russia to hold off any further aid to Assad and join the existing international coalition that has been fighting IS for a year.
"We've made clear that further support, military or otherwise, for the Assad regime is destabilizing and counter-productive, principally because Assad has lost the legitimacy to lead that country," White House spokesman Josh Earnest said. "Russia's decision to double down on Assad is a losing bet."
Sidelined in the increasingly fervent dialog with Moscow over Syria this month has been U.S. Defense Secretary Ash Carter. The Pentagon said that Carter has not spoken with his Russian counterparts since taking office at the beginning of the year, and is deferring to Kerry as the lead spokesman for the administration.
Lavrov earlier this week had called on Washington to re-establish communication between the military brass of both superpowers to avoid "unintended incidents" as each side goes its own way seeking to defeat IS in Syria.
The Pentagon says Moscow appears to be establishing a forward air operations base in Syria. U.S. officials have cited Russian deployments of artillery, tank, and other military hardware to a Syrian airfield.
The United States is using Syrian air space to lead a campaign of air strikes against IS, and a greater Russian presence on the ground raises the prospect of the Cold War superpower foes encountering each other on the battlefield.