US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov will return to Syria talks on Saturday with both sides having said that expectations for the meeting are not high.
The talks resume three weeks after the failure of their painstakingly drafted ceasefire that many saw as the last hope for peace this year.
Pressure is rising for a halt to a ferocious, three-week-old Syrian regime offensive to capture the opposition-held eastern zone of the city of Aleppo.
The United Nations says 275,000 civilians still live in the city and 8,000 opposition group members are holding out against Syrian regime, Russian and Iranian-backed forces.
Kerry has pointedly avoided new bilateral negotiations with Lavrov, and his invitation to the Turkish, Saudi, Qatari and Iranian foreign ministers to join them for talks in the Swiss lakeside town of Lausanne will broaden the discussion to include the most powerful backers of Syria's regime and opposition.
UN Syria envoy Staffan de Mistura is also attending the talks.
"I don't know that I would expect any breakthroughs. I would just say that we're working to get this multilateral effort and approach to Syria up and running," US State Department spokesman Mark Toner told reporters in Washington.
Russian news agencies on Friday quoted Lavrov as saying said that he had no "special expectations" for talks in Switzerland on the Syrian crisis.
Russian airpower is currently backing up Syrian regime forces in a ferocious assault on opposition-held eastern Aleppo that has sparked accusations of potential war crimes from the West.
The Syrian regime and Russia counter that they only targeting militants in Aleppo and accuse the United States of breaking the ceasefire by bombing scores of Syrian regime soldiers fighting Daesh, over which the United States has expressed "regret".
All sides will look at how to revive a short-lived ceasefire that Moscow and Washington hammered out, but Lavrov insisted Russia does not plan to present new initiatives on ways to resolve the conflict.
Instead he said Moscow would call for "concrete steps" to implement earlier UN resolutions and the now defunct US-Russia ceasefire deal.
Iran foreign minister to join Syria talks in Switzerland
Iran's Foreign Minister Mohammad Javad Zarif will take part in talks this weekend in Switzerland on the Syrian crisis, a spokesman confirmed on Friday.
"Foreign Minister Zarif will attend the international conference on the Syrian crisis in Lausanne," foreign ministry spokesman Bahram Qasemi said, according to the IRNA state news agency.
Iranian media had earlier reported that Iran, which is one of the main supporters of Syrian regime leader Bashar al-Assad, would not take part in the talks.
In a gesture of apparent desperation, Staffan de Mistura has offered to escort members of Jabhat Fateh al-Sham militant group out of Aleppo if that would entice the Syrian regime to forge a ceasefire with the remaining opposition groups.
Although Lavrov has said he does not plan to bring any new ideas to Lausanne, but his deputy Gennady Gatilov said Russia wants to discuss de Mistura's offer, as well as elements of last month's failed truce deal, namely humanitarian aid deliveries and a pullout of both sides' troops from the Castello Road, a key supply route.
"And it's about time to start moving toward an inclusive political process," Gatilov told Interfax news agency.
The Syrian conflict, which began in 2011, has killed more than 300,000 people, created the world's worst refugee crisis, allowed for the rise of Daesh and drawn in regional and major powers.