MONTREUX - Syrian peace talks begin in Switzerland Wednesday, with officials expressing little hope of a major breakthrough beyond the feat of bringing President Bashar al-Assad's regime and the opposition to the same table.
International diplomats and Syria's warring sides arrived Tuesday for the crucial peace conference, after months of wrangling that had threatened to derail the talks up until the last minute.
US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov landed for the talks set to begin in the town of Montreux on Lake Geneva.
Delegations from the Syrian opposition and the Damascus regime also made it to Montreux, after the Syrian government plane was blocked for several hours from leaving Athens airport.
British Foreign Secretary William Hague, also attending the talks, called upon all sides involved in Syria's bloody civil war to "seize the chance" for peace.
Federico Lombardi, spokesman for the Vatican which sent a delegation, said; "just the fact they are meeting and beginning to talk is something".
Other international officials were similarly careful not to raise hopes.
"I don't think anyone who's dealt with Syrian officials has any false expectations of rapid progress," a senior US State Department official said.
"Everybody has to understand that this is the beginning of a process. It's not going to be fast. It's very bitter fighting on the ground. And so there's going to be an absolute requirement for patience and for persistence," the official added.
There were stark reminders of the Syrian conflict's impact in the run-up to the talks, with a bombing in Beirut that left four dead and new evidence alleging that Assad's forces have systematically killed and tortured thousands.
The so-called Geneva II conference was going ahead after a last-minute reversal saw UN leader Ban Ki-moon withdraw an invitation to Iran, less than 24 hours after he had announced it.
Syria's opposition had threatened to boycott the talks if Iran, a key backer of the Assad regime, took part.
This week's talks will be the most intensive diplomatic effort yet to resolve Syria's civil war, which after nearly three years has left 130,000 dead and millions forced from their homes.
Arriving for the talks, Syrian Foreign Minister Walid Muallem dismissed opposition demands for Assad to step down.
"The issues of the president and the regime are red lines for us and for the Syrian people," he was quoted as saying by the official SANA news agency.
"Nobody can touch the presidency."
German Foreign Minister Frank-Walter Steinmeier spoke of "measured expectations" and "small steps".
It took months of discussions to convince all sides to take part, with the main opposition group, the Syrian National Coalition, only agreeing at the eleventh hour.
Deep divisions within the opposition were exposed and questions have been raised about whether its delegation will be truly representative of Assad's opponents.
The biggest bloc in Syria's opposition-in-exile, the Syrian National Council, said Monday it was quitting the coalition because taking part in the talks would renege on its "commitments" to not enter negotiations until Assad left power.
In an AFP interview published Monday, Assad bluntly ruled out a power-sharing deal. He insisted the peace conference should focus on what he called his "war against terrorism".
After the launch of the conference in Montreux, which will also bring together some 40 countries and regional bodies, the Syrian government and opposition are to start separate talks in Geneva on Friday.
A source in the Russian delegation said Tuesday the direct talks could last seven to 10 days.
Highlighting the difficulties in bringing everyone together, the plane carrying the Syrian delegation was delayed for five hours in Athens on its way to the conference.
A Syrian official source said Greek authorities had initially refused to refuel the plane, while a Greek civil aviation spokesman said it had been inspected and that a flight plan had not been submitted.
The violence in and around Syria continued unabated, with reports of a regime air strike in Aleppo killing at least 10 people and a suicide car bomb killing four in neighbouring Lebanon.
The Beirut bombing was the latest in a string of attacks targeting strongholds of Lebanon's powerful Shiite movement and Syria ally Hezbollah, and was quickly claimed by a group believed to be linked to Al-Qaeda's Syrian arm.
Former international prosecutors meanwhile said Tuesday they had evidence from a defector proving that the Assad regime has systematically killed and tortured around 11,000 people.
The report, which was first released in The Guardian newspaper, CNN and Turkey's Anatolia news agency, shows evidence of starvation, strangulation and beatings, and features pictures of emaciated corpses with grisly wounds.
One of its authors - the former chief prosecutor of the special court for Sierra Leone, Desmond de Silva - said it was the "smoking gun" showing evidence of "industrial-scale" killing by the Syrian regime.