The PKK terrorist group's Syrian branch YPG poses a threat to not only Syria's territorial integrity but Turkey's national security as well, Turkey told the United States on Thursday.

Turkish Deputy Foreign Minister Sedat Önal had a phone call with U.S. Ambassador to U.N. Linda Thomas-Greenfield, who was visiting Turkey's southern Hatay province that borders Syria, upon her request, according to a statement by the Turkish Foreign Ministry.

Washington's envoy thanked Önal for Turkey's efforts to find a permanent and sustainable solution to the Syrian crisis. During the phone conversation, Thomas-Greenfield also voiced concern over Turkey's possible fresh operation in northern Syria amid the growing threat of the terrorist YPG/PKK in the region.

Önal emphasized that the YPG/PKK terrorist group poses an existential threat not only to Syria's territorial integrity but also to Turkey's national security.

He also reminded the U.S. envoy of Turkey's separate unfulfilled agreements with the U.S. and Russia on the elimination of terrorists in northern Syria back in October 2019, according to the statement.

The Turkish official said Ankara cannot be expected to stand idle amid increased terrorist attacks recently targeting Turkey from northern Syria.

Önal further told the U.S. official that Turkey will not sit by as the terrorist group spreads its separatist agenda within the country.

"We will continue to take the necessary measures against terrorist organizations that threaten our vital national security interests," he vowed.

In October 2019, Russia expressed commitment to removing the YPG/PKK from Tal Rifaat and Manbij after reaching an agreement with Turkey during Operation Peace Spring.

Moscow also promised that the terrorists would be removed 30 kilometers (18.6 miles) from the border on the M4 road and in the area outside the Operation Peace Spring area.

Likewise, then U.S. Vice President Mike Pence pledged to Turkey that the YPG/PKK terrorist group would withdraw from the region of Operation Peace Spring.

Turkey, which has mounted four operations in northern Syria since 2016, has vowed a new operation against YPG terrorists that control swathes of territory near the Turkish border.

While Turkey views the YPG forces in Syria as terrorists and a national security threat, the United States views the group as an ally that has helped drive Daesh from vast areas of Syria.

Washington, whose support for the YPG has long been a point of tension in ties with its NATO ally Turkey, has expressed concern, saying any new operation would put at risk U.S. troops – which have a presence in Syria – and undermine regional stability.

U.S. Secretary of State Antony Blinken on Wednesday warned NATO ally Turkey against a military operation in Syria, saying it would put the region at risk.

During a visit to the Turkish town of Hatay near the Syrian border, the U.S. ambassador to the United Nations reiterated U.S. opposition to any military action.

"We have engaged with the Turkish government. We have indicated our opposition to any decision to take military action on the Syrian side of the border. We think that nothing should be done to break the cease-fire lines that have already been established," Linda Thomas-Greenfield said.

She added that any such action would not only increase suffering but also the number of displaced people, including some who might try to cross the border into Turkey.

Erdoğan said on Wednesday Turkey would rid Syria's Tal Rifaat and Manbij areas of terrorists, confirming the targets of the operation and saying it would continue into other regions.

"We are taking another step in establishing a 30-kilometer (19-mile) security zone along our southern border. We will clean up Tal Rifaat and Manbij", he said, referring to two northern Syrian cities.

Erdoğan said they would then proceed "step by step, into other regions."

Turkey views the YPG as an extension of the PKK, which has been waging an insurgency since 1984 in which more than 40,000 people have been killed. Western governments, including the United States and European Union, designate the PKK as a terrorist organization./DS