WASHINGTON (AP) — Secretary of State John Kerry says prospects are uncertain at best for this weekend's Syria peace talks. But he says the diplomatic effort to end the war cannot be abandoned.

Kerry said Thursday that although the elements necessary to forge peace may not exist, "time and turbulence" can create new possibilities that must be explored.

His comments came as he prepared to leave Washington for Saturday's Syria meetings in Vienna.

Those meetings are aimed at starting a political transition process that participants say is critical to halting the crisis.

However, Kerry acknowledged that participants have to bridge vast differences to succeed, saying those involved are not on "the threshold" of an agreement.

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