Secretary of State Mike Pompeo on Tuesday accused Turkey of undermining the cohesion of NATO and opposing the principles of the alliance, the Greek newspaper Kathimerini reported, citing diplomatic sources.

Pompeo’s made the remarks during a teleconference of NATO foreign ministers, during which the U.S. secretary of state spoke of what he called Turkey’s provocative activities in Libya, Syria, Nagorno-Karabakh and the eastern Mediterranean.

Pompeo also referred to Turkey’s purchase of the Russian S-400 missile defense system, saying it was a “gift’’ from Moscow, according to the sources cited by Kathimerini.

In recent months, Turkish armed forces have launched major cross-border offensives against Kurdish armed groups in Syria, intervened against the UAE-backed strongman Khalifa Haftar in Libya, backed Azerbaijan in its aggressive attacks on Karabakh and confronted Greece over disputed maritime boundaries in the eastern Mediterranean.

During Tuesday’s teleconference, Pompeo also accused Ankara of the failure of the military “deconfliction mechanism” agreed upon between Turkey and Greece in October, Kathimerini said.

On Oct. 1, NATO confirmed that Ankara and Athens had agreed to “a bilateral military deconfliction mechanism” that would prevent a military confrontation over hydrocarbon resources in the eastern Mediterranean.

Ahead of Tuesday’s foreign ministers’ conference, the U.S. Ambassador to NATO, Key Bailey Hutchinson singled out Turkey’s behavior in the Eastern Mediterranean, the Nagorno-Karabakh conflict and the acquisition of the S-400 as problematic to the alliance.

“Some of the behaviour that has been mentioned is problematic to the unity of the alliance and the alliance is strong because we are unified. We are concerned most especially about the S-400,” she told the Abu-Dhabi-based The National.

“The idea that you can put a Russian-made missile defense system in the middle of our alliance is out of bounds. We have registered that with Turkey time and again,” Hutchison told The National on Monday.

“We hope before Turkey turns on that missile defense system that they will understand the consequences and how much it will hurt their alliance inter-operability with the rest of us,” added Hutchinson. “We hope that Turkey turns back the decision that they made in error to put a Russian missile defense system in Ankara. Many of us are trying to work with Turkey in a way that would cement our alliance unity and we are asking Turkey once again to be the great ally that they have been in the past.”