Greek Prime Minister Kyriakos Mitsotakis says his country is planning to exercise its legal right to extend its territorial waters along its western coastline from six to 12 nautical miles.
The plan was announced as Greece remains locked in a tense dispute with Turkey over maritime boundaries and energy rights in the eastern Mediterranean.
Turkey has a research vessel doing surveying work in waters claimed by both countries, which sent warships and held military exercises in the area.
The planned extension along Greece’s Italy-facing coastline would not directly affect the territory at the centre of the Greek-Turkish dispute. But Mr Mitsotakis told the Greek parliament that Greece is abandoning decades of “passive” foreign policy.