Turkey’s navy has issued an advisory saying that the Turkish ship Oruc Reis will carry out a seismic survey in the eastern Mediterranean over the next two weeks, a step likely to revive tensions with NATO ally Greece.

The two countries are at odds over overlapping claims for hydrocarbon resources in the region. A similar advisory, or Navtex, last month caused a row which was calmed after the intervention of German Chancellor Angela Merkel.

However, President Tayyip Erdogan said on Friday Turkey had resumed energy exploration work in the region as Greece had not kept its promises on the issue.

“We have started drilling work again,” said Erdogan, adding “I don’t think we are obligated to talk to those who do not have rights in the areas of maritime powers.”

Seismic surveys are part of preparatory work for potential hydrocarbon exploration. Turkey and Greece are also at odds over issues such as overflights in the Aegean Sea and ethnically divided Cyprus.