International mediator Lakhdar Brahimi will meet the two Syrian delegations for a further round of talks in Geneva on Friday, the United Nations said, hours after he met senior US and Russian officials to reinvigorate the talks process.

But opposition delegate Badr Jamous, following a meeting with US Under Secretary Wendy Sherman, said her meeting with Brahimi and Russian Deputy Foreign Minister Gennady Gatilov was "not successful".

"She just told us about the meeting with the Russians and Brahimi and it was not successful," he told reporters.

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