The first day of the Geneva II peace talks between the Syrian government and the opposition was characterized by bitter accusations, the BBC reports.
The opposition and the United States said that Syrian President Bashar Al-Assad had no legitimacy and must step down from power, while Syria's foreign minister exchanged words with UN Secretary-General Ban Ki-moon over the length of his speech.
Wednesday's initial meeting involved speeches from 40 or so foreign ministers and the direct talks between the sides are scheduled to begin in Geneva on Friday.
At a fractious evening news conference, during which there were repeated calls for calm, Ban spoke of the suffering in Syria, saying, according to the BBC, “Enough is enough. The time has come to negotiate."
He added that "the really hard work begins on Friday", adding, "We have a difficult road ahead, but it can be done and it must be done."
Ban dwelt on the Geneva communiqué, which calls for a transitional government in Syria, saying he was disappointed with the attitudes of both the Syrian government and its ally, Iran.
Earlier this week, Ban withdrew his invitation to Iran to attend the conference, after Tehran refused to adopt the Geneva communiqué.
At his press conference, U.S. Secretary of State John Kerry stressed that the Geneva communiqué and its call for political transition was the paramount focus of the summit.
"Every delegation, with one exception, embraced the Geneva communiqué," he said, referring to the Syrian government.
"No-one has done more to make Syria a magnet for terrorists than Bashar Al-Assad," Kerry charged, according to the BBC. "You cannot save Syria with Bashar Al-Assad in power."
Syria's Foreign Minister Walid al-Muallem said some states attending the talks had "Syrian blood on their hands" and called the opposition "traitors."
"No-one in the world has the right to confer or withdraw the legitimacy of a president, a constitution or a law, except for the Syrians themselves," he was quoted as having told Kerry.
Muallem also got into a spat with Ban when he ran far over the allotted 10-minute slot for each speaker, ignoring the UN chief’s attempts to intervene.
"You live in New York. I live in Syria," Muallem told the UN Secretary-General when asked to hurry up and finish his speech.
"I have the right to give the Syrian version here. After three years of suffering, this is my right," he insisted.
The head of the Syrian National Coalition, Ahmad Jarba, meanwhile, was quoted by the BBC as having said the Syrian government must sign up to a deal to transfer powers from Assad.
Jarba said that this would be "the preamble to Bashar Al-Assad's resignation and his trial alongside all the criminals of his regime. For the Syrians, time is now blood."
Jarba also displayed a photograph taken from a report by three war crimes investigators which alleged systematic torture and execution of opposition detainees in Syria. The report was released on Tuesday but dismissed as not credible by Damascus.