By John Irish, Stephanie Nebehay and Tom Perry
GENEVA/BEIRUT (Reuters) - Syria's fragile peace talks might not resume for at least a year if they are abandoned now, a senior Western diplomat warned on Wednesday, as the opposition urged more military support for rebels after declaring a truce was over.
Intense fighting in Syria has left a six-week-old ceasefire in tatters. The truce was brokered by the United States and Russia to pave the way for the first peace talks attended by the warring factions since fighting began five years ago.
Those talks, taking place under U.N. auspices in Geneva, also appear to have collapsed this week. The opposition says it has called a "pause" to negotiations, although it is reluctant to accept blame for the collapse by walking out altogether.
"If this ends now, it will be over for at least a year ... The Russians will steamroll -- taking advantage of a U.S. vacuum," the Western diplomat said, referring to fears Washington will be preoccupied by November's U.S. presidential election.
"There will be three million more refugees and thousands more dead," said the diplomat, who declined to be identified while describing a scenario world powers still hope to avoid. "If we all leave Geneva, I don’t see the process continuing.”
Damascus negotiators say the presidency of Bashar al-Assad is non-negotiable while the opposition sees removal of the president as a prerequisite and complains of no progress on an end to violence, humanitarian access and political detainees.
The Geneva talks aim to end a war that has killed more than 250,000 people, created the world's worst refugee crisis, allowed for the rise of the Islamic State group and drawn in regional and major powers. Russia's intervention in the conflict beginning late last year has swayed the war in Assad's favor.
The already widely violated truce began fraying more quickly some two weeks ago near Aleppo, where the Syrian army accused rebel groups of taking part in assaults by Islamists who are not covered by the ceasefire. Rebels say they were defending themselves from attacks by the army and its Shi'ite militia allies.
A total collapse of the Geneva talks would leave a diplomatic vacuum that could allow a further escalation of the war that is being fueled by rivalries between foreign powers including oil producers Iran and Saudi Arabia.
France said it would discuss with other European powers and the United States on Monday the idea of convening a ministerial meeting of major powers in the next two weeks to work out the next steps for Syria.
GIRDING FOR MORE BATTLE
As fighting raged and air strikes on rebel-held areas intensified, the opposition urged foreign states to supply them with the means to defend themselves, a thinly veiled reference to the anti-aircraft weapons long sought by insurgents.
Air strikes killed around 40 people in a crowded market on Tuesday in what may have been the worst incident of its kind since the cessation of hostilities took effect in February.
France said the government was rushing "headlong" into violence and showing its refusal to negotiate a political solution. Syrian state TV cited a military source denying any air force raids on residential areas.
Anas Al Abde, president of the Turkey-based opposition Syrian National Coalition, said the Geneva talks were "futile" and there was no hope in discussing political transition.
Speaking at a televised news conference in Istanbul, he urged "qualitative support" for rebel groups, and said the solution must be a "political-military" one.
U.N. envoy Staffan de Mistura has come closer than any mediator so far in bringing the warring sides to peace talks which began last month, after the implementation of the partial truce brokered by the Washington and Moscow.
But the sides have yet to narrow their differences on issues like the fate of Assad, and it will be difficult to lure the opposition back to the table if fighting resumes unchecked, with the government taking advantage of Russia's firepower.
On Wednesday experts were meeting in Geneva but the opposition's Riad Hijab, chief coordinator of the Saudi-backed High Negotiations Committee (HNC), had quit the talks with senior delegates while de Mistura had left for personal reasons. About half of the HNC delegation remained.
The Syrian government negotiator Bashar Ja'afari poured contempt on the opposition for its partial walkout, accusing it of sulking and political immaturity.
"They (High Negotiations Committee) do not represent the Syrian people. Quite on the contrary, by leaving they may be taking away a major obstacle that will allow us to reach a solution," he told reporters.
Russia said the opposition was incapable of reaching a deal. "By issuing ultimatums, the Riyadh group, it seems, is trying to mask the fact it has no concrete and realistic proposals," the foreign ministry said.
Randa Kassis, who heads up a Moscow-backed opposition group, said both sides wanted to impose their view. "The solution will have to come from outside: Russia, the U.S. and the Security Council," she said. "It will take a lot more time."
Rebel armed groups appear to be girding for more war. Fares al-Bayoush, a colonel who heads the Northern Division rebel group affiliated to the Western-backed Free Syrian Army told Reuters: "Our situation on the frontlines is acceptable, but we await the increase of the support, or as the states promised ... so we can force it (the regime) to resort to the political solution."
He said there would be no return to negotiations "soon".
States opposed to Assad have been channeling military support to vetted rebel groups via both Turkey and Jordan, in a program that has included military training overseen by the U.S. Central Intelligence Agency.
GRAVE CONCERNS AT NEW REFUGEE EXODUS
The United Nations expressed deep concern on Wednesday over the fate of Syrians who have fled fighting near the northern city of Aleppo.
More than 40,000 people in camps, residential areas and settlements have been displaced due to fighting in recent days, mostly pushed eastwards toward the strategically vital border town of Azaz, as well as the Bab al-Salam and Sijjou camps for internally-displaced, the United Nations said.
"Taking into account the previous influx of over 75,000 internally displaced people into the Azaz sub-district in January and February, humanitarian needs are expected to rise exponentially," the U.N. Office for Humanitarian Affairs (OCHA) said in an overnight update.
Previous rebel losses in the area near the Turkish border have made it difficult for international aid agencies to reach civilians, making it one of the areas of greatest concern for those trying to protect Syria's civilians from harm.
The opposition accuses the government of violating the cessation of hostilities to capture Aleppo, Syria's most populous city before the war, which has been divided between government-controlled and rebel-held zones for years.
The medical charity Medecins Sans Frontiers said there were now more than 100,000 people trapped on the Syrian side of the Turkish border, with 35,000 having fled in the past week from camps that had been taken over by Islamic State fighters or had become too close to the front line.
(Additional reporting by Lisa Barrington; writing by Peter Millership; editing by Peter Graff and Philippa Fletcher)