Turkish President Recep Tayyip Erdogan said Sunday that his country will carry out a military operation in northern Syria against Kurdish militia that it views as a "grave security threat."

The operation will be carried out east of the Euphrates river in northern Syria, an area controlled by the Kurdish People's Protection Units (YPG), the Turkish leader said in the northwestern city of Bursa during a motorway opening ceremony.

Turkey has been very frustrated with the United States, which made an agreement with Ankara to implement a safe zone in northern Syria.

Erdogan said both Russia and the United States had been informed of the operation.

Ankara has repeatedly requested the creation of a 20-mile (32 kilometers) safe zone in northern Syria and stressed that it wanted the YPG cleared from this area.

Following US President Donald Trump's announcement last year of a planned US withdrawal from northern Syria, the two NATO allies agreed to create a safe zone inside Syria along its northern border with Turkey.

The YPG was Washington's main ally on the ground in Syria during the battle against Islamic State (IS), but Turkey sees the YPG as the Syrian offshoot of the outlawed Kurdistan Workers' Party (PKK).

Ankara has slammed the United States for dispatching thousands of trucks carrying military equipment and weapons to the YPG.

Ankara accuses Washington of stalling progress on setting up the safe zone and has urged Washington to cut off its relations with the YPG.

There has also been disagreement between the two countries over the size of a safe zone and who will control it.

Thousands of army troops, including heavy weaponry, armored vehicles and tanks, have been sent and deployed in border areas in recent months in a prelude to a new incursion in Syria.

Contacted by Xinhua, the Turkish Defense Ministry declined to answer questions on a possible imminent offensive and said "no comment."

Last two weeks, US and Turkish military and civilian delegations held talks on the safe zone, but failed to reach an agreement.

"We have no patience left, we will have to create a safe zone on our own," Turkish Foreign Minister Mevlut Cavusoglu told reporters afterwards.

The new spat over a safe zone in Syria is the latest development in a long running disagreement between the two NATO allies.

Turkey has been skeptical of US support for Kurdish militia since the Gulf War in Iraq, seeing it as a move advocating a Kurdish independence.

Ankara fears now that the support given by the United States to the Syrian Kurds would lead in time to the formation of a Kurdish state at its borders.