The UN’s Syria envoy voiced hope Tuesday that peace talks could restart next month, as US Secretary of State John Kerry said there had been "progress" in efforts to salvage an urgently-needed ceasefire.

The UN's Syria envoy voiced hope Tuesday that peace talks could restart next month, as US Secretary of State John Kerry said there had been "progress" in efforts to salvage an urgently-needed ceasefire.

UN envoy Staffan de Mistura has struggled to keep the peace process alive amid a surge in fighting between Syrian President Bashar al-Assad and    terrorist groups.

De Mistura met with US Syria envoy Michael Ratney and deputy Russian foreign minister Gennady Gatilov, part of a bid to salvage diplomatic efforts to end more than five years of brutal conflict.

"Our aim is to proceed with a third round of intra-Syrian talks towards the end of August," de Mistura told reporters after the meeting.

While de Mistura has said he would prefer to negotiate with a real ceasefire in place, he conceded that may not be realistic.

"The talks are not going to wait for improvement in Aleppo or in Damascus," he said.

The Geneva meeting came hours after higher-level negotiations on the sidelines of an Asia summit in Laos.

In Vientiane, Kerry said Washington was "making progress" with Russia on Syria cooperation following a meeting with Russian counterpart Sergei Lavrov.

Russia and the United States support opposing sides in Syria's civil war, which has left 280,000 people dead and forced half the population to flee their homes.

Kerry held marathon talks with Russian President Vladimir Putin and Lavrov in Moscow last week.

They agreed "concrete steps" to revive the ceasefire and tackle 'jihadist' groups in Syria, although details have not been made public.

Kerry said Tuesday bilateral work was inching forward and that an updated diplomatic plan for Syria could be unveiled "somewhere in early August."

"What we're trying to do is strengthen the cessation of hostilities, provide a framework which allows us to actually get to the table and have a real negotiation," he said.