Syria's President Bashar Assad has conceded making mistakes and says no side in his country's civil war is entirely free of blame, according to an interview to be published Sunday by German magazine Der Spiegel.

The respected Hamburg-based weekly reported that Assad acknowledged "personal mistakes by individuals," though the advance version of the interview released Saturday didn't elaborate on what those mistakes might have been.

"We all make mistakes. Even a president makes mistakes," Der Spiegel quoted him as saying. Assad reportedly added that there were "gray tones" as far as the question of blame was concerned.

Assad, whose authoritarian rule prompted protests more than two years ago that evolved into a bloody civil war with over 100,000 dead, said he didn't believe in a negotiated peace with the rebels trying to oust him.

"According to my definition a political opposition isn't armed," he was quoted as saying.

In its announcement about the interview, Der Spiegel did not say when it took place or whether it was face to face.

The magazine reported that Assad had declared a willingness to call elections before his term ends in August, and that he hadn't yet decided whether to run for the presidency again.

"If I don't have the will of the people behind me then I won't run again," it quoted him as saying.

Asked about the Aug. 21 chemical weapons attack near Damascus that killed hundreds of people, Assad again denied his regime's involvement.

"The picture you're painting of me as someone who kills his own people is (false)," the magazine quoted him as saying.

Western officials, who say there is little doubt Assad's troops are to blame, "trust al-Qaida more than me," Assad reportedly said.