But, he noted Assad was not attending the summit.

The report came after four sources told Reuters Turkey's intelligence chief held multiple meetings with his Syrian counterpart in Damascus in recent weeks, a sign of Russian efforts to encourage a thaw between states on opposite sides of Syria's war.

Hurriyet columnist Abdulkadir Selvi reported Erdogan made the comments about Assad at a meeting of his ruling AK Party, held behind closed doors on Monday.

"I wish Assad had come to Uzbekistan, I would have spoken to him. But he can't come there," Erdogan was quoted by Selvi as saying at the party meeting.

"He went to war with rebels to maintain his own power. He chose to protect his own power. He thought to protect the areas he controlled. But he couldn't protect large areas," Erdogan was reported as saying.

Any normalisation between Ankara and Damascus would reshape the decade-long Syrian war.

Turkish backing has been vital to sustaining Syrian rebels in their last major territorial foothold in the northwest, after Assad defeated the insurgency across the rest of the country, aided by Russia and Iran.