Turkish President Tayyip Erdogan announced on Sunday that no other countries would be permitted by Ankara to drill for natural gas off the coast of Cyprus in the eastern Mediterranean sea. According to a report from Reuters, Erdogan made the announcement while attending the christening of two new Turkish warships — a submarine and a corvette.

“We will not accept attempts to extract natural resources in our country, Cyprus or in the eastern Mediterranean,” Erdogan said during the speech, according to Reuters.

Experts believe that the eastern Mediterranean Sea has sizeable natural gas reserves ripe for extracting; however, the promise of an abundant energy supply has made the region hotly contested — especially between Turkey and Greece.

Relations between the two countries are strained over the issue of Cyprus, a country that remains divided between the Greek and Turkish populations. Although once a united country, Cyprus has been divided since 1974 after Turkey invaded the country. Today, the Greek-backed government in the south is recognized by the world, but Ankara is the only government which acknowledges the Turkish-backed leadership in the north.