Diplomatic Push To End Bloody Conflict A diplomatic battle to end Syria's bloody civil war begins in Switzerland today as opposition delegates sit down with government representatives for the first time in three years. International delegates have gathered in the city of Montreux, on the banks of Lake Geneva, for talks aimed at ending a conflict which has killed more than 100,000 people. The peace talks will go ahead despite a last-minute dispute over the United Nations' decision to withdraw an invitation to Iran. The exclusion of the Islamic Republic from the conference has highlighted tensions between the West and Russia over how to broker an agreement to end the violence. Iran is the main ally of Syrian President Bashar al Assad. The country's exclusion came after Tehran refused to endorse a UN-backed plan for a transitional governing body in Syria. The city of Montreux, in Switzerland, will host the Geneva 2 talks The issue of transition of power is expected to be central to the success of the talks, which have been dubbed "Geneva 2." The Western-backed opposition has demanded that Mr Assad must quit and face a war crimes trial. But the Syrian Foreign Minister, Walid al Moualem, has rejected any discussion of Mr Assad being forced to step down. "The subject of the president and the regime is a red line for us and the Syrian people and will not be touched," he said on the eve of the talks, according to the SANA news agency. The conference also begins in the shadow of allegations of large-scale torture and execution of prisoners by government forces. US Secretary of State arrives in Switzerland ahead of the talks The day before the talks, a group of international lawyers published allegations of the "systematic torture and killing" of up to 11,000 people by the Syrian regime. Fatima Khan, the mother of British doctor Abbas Khan, who died in a Syrian prison last month, told Sky News' Joe Tidy that the reports of torture and execution were no surprise. I'm not surprised with the report. I knew ... all this," she said. I heard my son was living with 9,000 other prisoners and my son told me that every day they used to take two or three (and) torture them. Fatima Khan said allegations of torture in Syria were "no surprise" Either one comes back or two comes back, or none of the three comes back. I knew this. My son was only a humanitarian aid worker. Why was he tortured? If that regime is so cruel (that) they have no brains and no heart to understand (the difference between) a humanitarian aid worker and a terrorist, then they should not stay in power. Foreign Secretary William Hague urged both sides in Syria to "seize the chance" to end the civil war as he arrived in Switzerland. Opposition has been tested and has come. Now regime must be tested on willingness to seek a political solution," Mr Hague wrote on Twitter. Smoke rises after a bomb blast in the Syrian city of Aleppo Mr Hague added that it was a "great shame" that Iran - which has enjoyed a thawing of relations with the West in recent months - had failed to endorse the principles of the talks. US President Barack Obama and Russia's Vladimir Putin had a "business-like" conversation about the Syrian conflict by phone on Tuesday. Russian Foreign Minister Sergei Lavrov also met US Secretary of State John Kerry in Montreux ahead of today's opening of negotiations.