Censor.NET reports citing AFP (via Business Insider).
The envoys from Washington, Riyadh and Ankara -- all of which back groups battling against Assad -- will look to sound out Russian Foreign Minister Sergei Lavrov in Vienna after the embattled Syrian strongman made a surprise visit to Moscow to meet President Vladimir Putin this week.
Assad's fate remains a major a stumbling block in the talks, AFP reports.
Washington and its regional allies have long insisted Assad has to go for there to be any chance of a political solution to fighting that has cost more than 250,000 lives, but Moscow says it must first help him defeat IS and other "terrorists" before talks can start on any reforms.
"The aim of the US is to get rid of Assad, probably that is so, our aim is to defeat terrorism, to battle terror, and to help President Assad claim victory over terror," Putin said Thursday in the Black Sea resort of Sochi.
"In this way, we can then create the conditions for the start and, I hope the successful reaching of a conclusion, of the political process to find a settlement."
Meanwhile, US Secretary of State John Kerry said in Berlin that while all sides agreed on the need to find a political solution and battle IS only "one thing stands in the way... a person called Assad -- Bashar al-Assad".
Assad's surprise visit to Moscow on Tuesday -- his first known trip abroad since the start of the Syrian conflict in 2011 -- has now placed the Kremlin as the key link to the strongman, AFP reports.
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