Syrian opposition negotiator Mohamad Alloush says Syria's political transition can only start once Bashar al-Assad is no longer president of Syria.
"We consider that the transitional period starts with the fall of Bashar al-Assad or his death," he told reporters in Geneva on Saturday, where a round of peace talks is due to begin on Monday.
"There's no possibility to start this period with the presence of this regime or the head of this regime in the power."
He described as "worthless" a statement by Syrian Foreign Minister Walid al-Moualem earlier on Saturday that the presidency was not up for discussion at the talks.
"We will not talk to anyone who talks about the position of the presidency. Bashar is a red line, the property of the Syrian people," Moualem said during a televised news conference in Damascus.
"I advise them that if this is their thinking, they shouldn't come to the talks.
"They must abandon these delusions."
The Syrian Civil War started when pro-democracy protests erupted in 2011. After government security forces opened fire on demonstrators, nationwide protests were triggered that demanded Assad's resignation.
Violence escalated and the country descended into war as rebel brigades were formed to battle Assad's forces, who have more recently been bolstered considerably by Russian air support.
All parties to the conflict have committed war crimes, according to the UN, including murder, torture, rape and enforced disappearances.
Assad's forces are also believed to have carried out chemical weapons attacks on civilians. In Feburary, the UN reported that Assad's regime has killed so many detainees that it amounts to the crime against humanity of 'extermination'.
More than 250,000 Syrians have died in the conflict and more than 11 million others have been displaced.
AAP / Newshub.