The UN envoy for Syria on Friday joined a closely-watched meeting between Russia and the United States, raising hopes for progress towards resuming peace talks for the war-ravaged country.

The UN envoy for Syria on Friday joined a closely-watched meeting between Russia and the United States, raising hopes for progress towards resuming peace talks for the war-ravaged country.

Staffan de Mistura arrived shortly before 1:00 pm (1100 GMT) at a Geneva luxury hotel where US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov had been meeting since mid-morning.

Their talks were expected to centre heavily on Syria's devastating conflict, with de Mistura hinting Thursday the discussion would be "important", and could help his drive to restart peace talks.

The UN envoy had voiced hope of bringing the warring parties back to the negotiating table by the end of August, but that deadline looks sure to slip in the face of intense fighting on the ground.

Successive rounds of international negotiations have failed to end a conflict that has killed more than 290,000 people and forced millions from their homes.

Friday morning, Kerry and Lavrov shook hands cordially before the cameras, but did not comment on what they expected from their meeting.

When asked by a reporter what they thought was the primary impediment to a ceasefire in Syria, Lavrov said: "I don't want to spoil the atmosphere for the negotiations."

Kerry, who flew in late Thursday from Jeddah in Saudi Arabia where he announced a new peace push for conflict-torn Yemen, made no comment.