GENEVA: Talks to end Syria's brutal five-year conflict were to resume in Geneva Wednesday, although the negotiations were likely to be overshadowed by a surge of violence that threatened a fragile truce.
Adding more tension, Syrians began voting in government-controlled areas in a parliamentary election which is not recognised by the United Nations or by President Bashar al-Assad's main opponents.
The UN-brokered talks in Geneva are aimed at forming a transitional government and a new constitution followed by general elections to end a conflict that has killed more than 270,000 people and displaced half of the country's population.
But Assad's fate remains a major stumbling block.
UN Syria envoy Staffan de Mistura met with Assad's key allies Tehran and Moscow ahead of a sit-down with the main opposition High Negotiations Committee on Wednesday afternoon and regime representatives later in the week, probably Friday.
Russian Foreign Minister Sergei Lavrov stressed the importance of this round of talks, which is scheduled to last about 10 days.
"The Syrian parties should discuss the new constitution, and how they see the structure that will ensure a peaceful transition towards a new system," he told reporters in Moscow.
A Western diplomat also said "there is more riding on this round" than previous rounds, since de Mistura is looking to concretely address the thorny issue of "what does transition away from Assad actually look like".
A surge in violence in recent days has however threatened a landmark ceasefire agreed in February and piled more pressure on these talks, which follow fruitless attempts in previous years to negotiate an end to the bloodshed.
"Right now, there are signs that this (the ceasefire) is slipping and it is a much more delicate environment for de Mistura to convene political talks," US Ambassador to the UN Samantha Power told reporters in New York after a briefing by de Mistura on Tuesday.
Power said Moscow must put pressure on Damascus to "get the regime back with the programme", adding she was "very alarmed" by Syria's plans to launch a Russian-backed counter-offensive in Aleppo, the epicentre of the renewed fighting.
Moscow began an air campaign in support of the regime last September, though last month Russia ordered the bulk of its forces to withdraw.
Wednesday's parliamentary elections in Syria, which caused the regime delegation to delay its arrival in Geneva for the talks, are also adding more pressure to the negotiations.
"The decision of the regime to hold elections is a measure of how divorced it is from reality. They cannot buy back legitimacy by putting up flimsy facade of democracy," a spokesman for the British government said Wednesday.
Lavrov however defended the elections, saying they would "ensure the functioning of state institutions... (Their) role is to not leave a (power) vacuum."
The vote is taking place in areas under government control -- around a third of Syrian territory where some 60 percent of the population lives -- and is expected to see Assad's Baath party maintain control over parliament.
The partial truce brokered by Moscow and Washington, which came into effect on February 27, had raised hopes for a resolution to the conflict, until the recent escalation in fighting in northern Aleppo province, in parts of Hama province and Damascus.
The truce has brought about a significant drop in civilian deaths and permitted increased aid deliveries to besieged and hard-to-reach areas, although humanitarian access has recently slowed again to a crawl.
Pro-government forces were on Tuesday pressing an advance against the town of Al-Eis, held by Al-Qaeda's local affiliate, Al-Nusra Front, and allied rebels, the Syrian Observatory for Human Rights said.
Jihadists like those from Al-Nusra and the Islamic State group are excluded from the ceasefire. But in some areas, Al-Nusra is allied with rebel forces meant to be covered by the truce.
Washington voiced concern Monday that an assault on Al-Nusra in Aleppo could spread to more moderate factions, and cause the truce to collapse and derail the peace efforts.
"We are concerned about plans to attack and seize... Aleppo when there are clearly opposition groups there that are part of the cessation of hostilities," State Department spokesman Mark Toner told reporters.