US Secretary of State John Kerry said Wednesday that this week’s international talks on the war in Syria will not find an immediate political solution but nevertheless represent the best hope available.

US Secretary of State John Kerry said Wednesday that this week's international talks on the war in Syria will not find an immediate political solution but nevertheless represent the best hope available.

"While finding a way forward on Syria will not be easy -- it's not going to be automatic -- it is the most promising opportunity for a political opening we have seen," he said in a speech on Middle East policy just before he was to set off for Vienna.

"My friends, the challenge that we face in Syria today is nothing less than to chart a course out of hell."

Kerry was to meet with his counterparts from a dozen world powers in the Austrian capital for a series of bilateral and multilateral talks on Thursday and Friday to find consensus on a political way forward in Syria.

Speaking to the Carnegie Endowment for International Peace, Kerry noted that Iran is to take part for the first time, along with Russia.

"But it is also clear that Russia and the United States share an amazing amount of common ground on this," he said, arguing that both want "a united, secular Syria" in which citizens can choose their own leader through elections.

"We agree that all of these steps can only be achieved, and Syria can only be saved, through a political settlement," he said, arguing that "one man" -- Assad -- cannot be allowed to stand in the way of peace.

"Ultimately, to defeat Daesh, we have to end the war in Syria, and that is America's goal," Kerry said, using a term for the Takfiri group, ISIL (so-called Islamic State in Iraq and Levant), based on its Arabic acronym.

The Vienna discussions are expected to be the first time all major international players in the conflict, linked to the nearly five-year war, will participate.