"President Assad has nothing to do with the... talks," lead government negotiator Bashar al-Jaafari told journalists.
Jaafari insisted that political transition in the war-ravaged country and Assad's fate were "two separate issues."
"The references of our talks do not give any indication whatsoever with regard to the president of the Syrian Arab Republic," he said.
Assad's future "is something that is already excluded from the scene", Jaafari said, following his meeting with United Nations mediator Staffan de Mistura.
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The main opposition High Negotiations Committee (HNC) has made Assad's departure a non-negotiable demand before any peace deal can be agreed.
De Mistura has described political transition as "the mother of all issues" standing in the way of a breakthrough, but has not directly addressed the Assad question.
As the talks entered their second week, Jaafari said the atmosphere was "positive," even if progress was "lagging", while charging the HNC with not doing its part.
"We have clear instructions from our leadership to engage seriously in these talks but the other side is not responding seriously," Jaafari said.
De Mistura on Friday said he has been urging the regime to submit concrete proposals for its vision of a transition government that could lead Syria out of five-years of brutal conflict.
Jaafari countered on Monday that his side had given the UN a document addressing principles for a political solution to the conflict.