Turkey's Foreign Minister Mevlut Cavusoglu said on Monday that if a planned safe zone in northern Syria is not established, and if threats continue against Turkey, Ankara will launch a military operation east of the Euphrates river.

Turkey has been in talks with the United States over the establishment of a safe zone across its border in northeast Syria, where the US supports the Kurdish YPG militia. Ankara sees the YPG as a terrorist organisation.

In an interview with broadcaster TGRT Haber, Cavusoglu also said he hopes an agreement will be reached after talks on Monday with US special envoy for Syria James Jeffrey, who is visiting Turkey.

Ankara wants YPG fighters to withdraw from the border area, while Washington wants guarantees that its Kurdish-led allies in the campaign to defeat Islamic State in Syria will not be harmed.

Cavusoglu said that talks with the US on the safe zone have slowed, adding that Turkey had told Washington that it should not use the fighting in Syria's northwestern Idlib province as a pretext for disregarding the proposed safe zone further east.

He repeated Turkey's frustration that a deal with the US for the withdrawal of YPG forces from the town of Manbij had still not been implemented, more than a year after it was agreed, and warned that Turkey will act unilaterally if talks on the safe zone stall.

"If the safe zone is not established and threats towards our country continue, we will launch the operation in the east of the Euphrates," he said.

"The Americans sent Jeffrey and said there were new proposals in the talks that will start today. We hope an agreement can be reached on this. Concrete steps are needed on this now."