Russia's foreign ministry, meanwhile, has accused the Obama administration of applying a "scorched earth tactic" to US-Russian relations and of using "lies" to portray Russia as an enemy.

With no let-up in Syrian President Bashar al-Assad's onslaught on eastern Aleppo, the sides will look at how to revive a short-lived ceasefire.

Russia and the United States reached an agreement before it quickly collapsed amid the Syrian assault on the rebel-held part of the city, backed by Russian air power.

Kerry and Lavrov, once joint sponsors of worldwide peace effort, met ahead of the broader talks, but U.S. officials insisted that their "bilateral track" remains dead. For all the talk in Washington about a possible Plan B, USA hopes for diplomatic progress appeared to rest squarely on Russia's co-operation.

But a senior U.S. official, travelling with Kerry, told reporters that the talks were created to explore ideas for ending the conflict not to produce an immediate breakthrough.

But it's unclear how the larger format for discussions would change Russia's calculus.

But both U.S. and Russian officials played down hopes of a breakthrough on Saturday, and Kerry was due to fly on to London on Sunday to brief European allies on the new effort.

"I don't have any particular expectations", Lavrov said Friday in Moscow, putting a damper on prospects for a positive outcome.

United Nations special envoy Staffan de Mistura, Iran's chief diplomat Mohammad Javad Zarif, and foreign ministers from rebel-backing countries like Qatar are also expected to attend.

Churkin made the point that the meeting needs to be smaller than the ones that have taken place with the International Syria Support Group (ISSG), saying, "You know how it happens, everyone wants to get in so it became a large group of people, very hard to talk and very hard to come up with something specific".

Abdal Ahad Stefo, deputy head of the Istanbul-based National Coalition, told AFP the negotiations "will only lead to wasting more time".

"I think we need to see what happens in the room to determine whether this is the beginning of a new process that continues in this format or not", said a senior U.S. official travelling with Kerry, who arrived in Lausanne at around 0900 GMT.

On Friday, Lavrov had warned that Russian Federation was not planning on presenting new initiatives on ways to resolve the conflict, which has claimed more than 300,000 lives since 2011.

Russian President Vladimir Putin [official website] rejected suggestions that his country could face war crimes charges because of its role in the airstrikes in Aleppo, Syria.

Speaking to CNN's Christiane Amanpour, Mr Lavrov said Russian Federation welcomed the proposal by the United Nation's special envoy for Syria Staffan de Mistura to personally escort the estimated 900 fighters from Jabhat Fatah Al Sham - formerly Al Qaeda's Syrian affiliate - out of Aleppo.

It dissolved after barely a week and the USA ended bilateral talks with Russian Federation after a series of airstrikes led to recriminations from both sides: Russian Federation condemned a US airstrike on Syrian government troops, who the Americans said were mistaken for ISIS targets; the USA said Russian Federation was responsible for a drone strike on a humanitarian aid convoy.

"We've asked countries to come, having done some thinking, about a realistic way forward given the differences represented in the room", a senior US State Department official said.

The nongovernmental organisations issued on Saturday a joint plea "to establish a ceasefire of at least 72 hours in east Aleppo", where an estimated 250,000 people are living under bombardment siege. Scores of people, including children, died in the assault.

A Syrian civil defence volunteer, known as the White Helmets, stands on the rubble of destroyed buildings during a rescue operation following regime air strike on the opposition-held neighbourhood of Bustan al-Basha in Aleppo.

President Vladimir Putin this week pledged that Russian Federation won't give in to "blackmail and pressure" over its campaign in Syria, which also incorporates Shiite fighters backed by Iran and Hezbollah.

It comes nearly two weeks after the USA suspended dialogue with Russian Federation over Syria after an intensification of air strikes on Aleppo.

Syria and Russian Federation counter that they only targeting militants in Aleppo and accuse the United States of breaking the ceasefire by bombing scores of Syrian troops fighting Islamic State insurgents, over which the United States has expressed "regret".

He said the other remaining rebel stronghold of Idlib, about 60 kilometers southwest of Aleppo, would be the next objective.

Vitaly Churkin said Friday that Russian Foreign Minister Sergey Lavrov and U.S. Secretary of State John Kerry will be joined in Lausanne, Switzerland by ministers from several countries that are "really, really, really influential" with opposition fighters.