Greece plans to extend its territorial waters further, including potentially in the Aegean Sea, Foreign Minister George Gerapetritis said on Friday, despite Turkey’s long-standing threat of war should Athens take such a step.

The NATO allies, but historic rivals, have eased tensions in recent years but remain at odds over where their continental shelves begin and end in the Aegean, an area believed to hold significant energy potential and with implications for overflights and airspace.

Greece has already extended its territorial waters in the Ionian Sea to 12 nautical miles from six, following agreements with Italy, and it has signed a maritime delimitation deal with Egypt in the eastern Mediterranean.

But it has avoided similar moves in the Aegean, where Ankara objected sharply.

In 1995, the Turkish parliament declared a “casus belli”, or cause for war, if Greece unilaterally extended its waters beyond six nautical miles in the Aegean, a position Athens says violates international maritime law.

Answering questions in parliament on Friday, Gerapetritis said further expansion was expected.

“Today, our sovereignty in the Aegean Sea extends to six nautical miles,” Gerapetritis said. “As there was an agreement with Egypt, as there was an agreement with Italy, there will also be a (further) extension of the territorial waters.”

He didn’t specify which maritime areas could be extended.

Turkey’s Foreign Ministry was not immediately available for comment.

In July, Greece took another step by unveiling the boundaries of two planned marine parks in the Ionian and Aegean seas.

The Aegean park, covering 3,668 square miles, would initially expand around the southern Cyclades islands, further south of Turkey, according to the maps submitted by Athens. The announcement has drawn objections from Ankara.

Greece says the only issue it is prepared to discuss with Turkey is the demarcation of their maritime zones, including the continental shelf and an exclusive economic zone.