NATO will continue its efforts to help reduce tensions between Greece and Turkey in the Mediterranean, the alliance's chief said Wednesday.

Speaking at a news conference in Brussels ahead of a virtual meeting of NATO defense ministers, Secretary-General Jens Stoltenberg said the alliance had helped establish a hotline between Greece and Turkey, using NATO communication systems and secure networks 24/7 if needed.

He added that NATO was looking into how to strengthen the deconfliction mechanisms to minimize the risks of incidents and accidents in the region.

"And we also strongly believe that the deconfliction efforts in NATO, which takes place inside its headquarters as a military technical work, is helpful also to support the German-led efforts to facilitate exploratory talks about the underlying main dispute in the Eastern Mediterranean," he said.

"The more we succeed with deconfliction, I think the more we are supporting the German efforts to facilitate talks," he added.

Stoltenberg also said that he was in regular contact with EU officials, including European Council President Charles Michel, European Commission President Ursula von der Leyen and foreign policy chief Josep Borrell, as well as the leaders of EU member states.

"I know that the ambition of reducing tensions of deconfliction is a shared ambition by NATO and the European Union," he added.

S-400 missile defence systems

Stoltenberg also expressed concern over Turkey's decision to acquire S-400 missile defense systems.

Reiterating his support to find alternatives for the Russian-made S-400, he said: "Of course it is a national decision what kind of defense capabilities different allies acquire. But at the same time, what matters for NATO is interoperability and the importance of integrating Air and Missile Defense and that can not be the case with a Russian system S- 400."

Turkey holds that the S-400 would not be integrated into any NATO systems and would not pose any risk to the alliance.