BEIRUT (AP) -- Syrian President Bashar Assad said in remarks published on Monday that he was prepared "to negotiate everything" at talks set to begin in later this month in Kazakhstan, seeking to cast himself as a peacemaker after his forces' recapture of Aleppo last month.
However the upcoming talks, brokered by Ankara and Moscow, are still in doubt as Syrian opposition groups have yet to confirm their participation.
In comments to French press from his Damascus palace, Assad also defended his troops' deadly bombardment of eastern Aleppo, saying the alternative would have been to leave the city's civilians to the mercy of "terrorists" --- a term the government uses for all opposed to Assad's rule.
Assad questioned the credibility of Syrian opposition groups backed by the West and Saudi Arabia, which make up the bulk of the armed and political opposition to his rule.
"There's no limit to negotiations," Assad said. The remarks were carried by the Syrian state media. "But who is going to be there from the other side, we don't know yet. ... The viability of the conference depends on that."
Past Syrian peace talks have run aground on the question of Assad's future and whether he is to continue as president, with the opposition insisting his departure is the precondition for any reforms.
Assad insisted the matter could only be resolved through a constitutional referendum.
"My position is related to the constitution," he said. "If they want to discuss this point, they need to discuss the constitution. You need a referendum for every (constitutional amendment). This is one of the points that could be discussed in the meeting" in Kazakhstan.
The talks are scheduled to begin in the Kazakh capital of Astana on Jan. 23. They follow a lengthy rapprochement between Russia, a key backer of Assad, and Turkey, a main sponsor of the opposition, that culminated in a cease-fire agreement that came into force on Dec. 30, but that has already started to erode.
The U.S. is excluded from the talks, and Russian officials have suggested U.S. officials could be invited at a later date.
As for Aleppo, Assad said the government forces were forced "to liberate" the city.
"And there is a price, sometimes, but at the end the people are liberated from the terrorists," he added.
Once Syria's largest city and industrial hub, Aleppo has been devastated by nearly six years of war. Rebels took control of its eastern districts in 2012, before surrendering it to government authority last month.
The U.N. said the government's relentless military campaign, which displaced tens of thousands of civilians, could have violated the laws of war.