"This is a positive approach," Erdogan told reporters, when asked about Sunday's statement from US Pentagon chief Mark Esper.

Turkey is in the sixth day of an offensive against Kurdish forces in northern Syria.

It says it has seized control of two key towns, Tal Abyad and Ras al-Ain, although fighting was reported as ongoing in the latter.

Erdogan said he expected Kurdish forces to withdraw from other key towns such as Manbij.

"When Manbij is evacuated, we will not go in there as Turkey. Our Arab brothers, who are the real owners, the tribes... will return there. Our approach is to ensure their return and security there," he said.

He also said Russia -- a decisive actor in the multi-faceted Syria conflict as a key backer of Damascus -- was not putting obstacles in the way of an offensive on another key town, Kobani.

"There is a lot of gossip now, but it seems... there won't be any problem in Kobani with Russia's positive approach as of now," Erdogan said.

The Turkish president again criticised Western allies who have come out strongly against the operation. France, Germany and Italy are among those who have suspended arms shipments to Turkey over the issue.

"Who will you side with? With your NATO ally or terrorists? They cannot answer. It is not possible to understand the goal and reason of what they are doing," he said.

"I am thinking -- is it because Turkey is the only country in NATO whose people are Muslim?"

Erdogan's spokesman Ibrahim Kalin tweeted: "Those who remained silent while Mosul, Raqa, and Dier al-Zor were being torn down and thousands of civilians were killed are making 'Stop the operation' calls... and threatening Turkey with sanctions. There is no stop until we achieve our targets."