“What we now absolutely and immediately need are signs of de-escalation and a readiness for dialogue,” Maas said following a meeting with Greek Foreign Minister Nikos Dendias in the Greek capital.

The situation in the Mediterranean, where tensions have escalated due to Turkey’s energy exploration, amounts to “playing with fire,” Maas warned.

“Each spark, no matter how small, can lead to a catastrophe,” he added.

There are concerns that a military conflict could break out between NATO allies Greece and Turkey regarding disputed maritime borders in the area, which is believed to be rich in hydrocarbon resources.

Greece and the European Union say Turkey’s drilling for oil and natural gas in the region is illegal, while Turkey contests that the area is within its exclusive economic zone.

Turkey’s Oruc Reis research vessel is conducting the exploration work near Cyprus, accompanied by warships. It is currently to continue doing so until August 27, state news agency Anadolu has reported.

Greece has ruled out direct talks with Turkey so long as the Oruc Reis mission continues.

But late Monday, Erdogan held firm, saying: “Turkey will not take a single step back from the activities of our Oruc Reis vessel nor the navy forces accompanying it.”

The row has already led to a confrontation between a Turkish frigate and a Greek vessel in the region.

Germany has been seeking to mediate in the crisis for weeks now, with Chancellor Angela Merkel having conducted talks separately with Erdogan and Greek Prime Minister Kyriakos Mitsotakis.

“The windows for dialogue between Greece and Turkey must now be further opened and not closed. To do this, instead of new provocations, we need to take steps towards detente and enter into direct talks,” Maas said in a statement upon departing for Athens.

Later Tuesday, he is set to meet Turkish Foreign Minister Mevlut Cavusoglu in Ankara.

The talks come ahead of an EU foreign ministers conference set to take place on Thursday and Friday in Berlin.

The European Union is in a tricky situation as it tries to support member state Greece without angering Turkey too much.

Turkey is a key partner of the EU in stemming the flow of migrants to Europe.

So far, the EU has reacted with only moderate sanctions that have not really hurt Turkey.

Stricter measures would be, for example, suspending the customs union with Turkey.

Alternatively, the two sides could come to their own agreement on the maritime borders, or settle the dispute before the International Court of Justice in The Hague.