ATHENS/ANKARA - Germany warned on Tuesday that Greece and Turkey risked a military clash unless they turn to dialogue to solve a row over energy resources in the Mediterranean Sea, where the NATO allies geared for rival naval drills in disputed waters.Ankara and Athens have traded rhetorical barbs over offshore hydrocarbon rights, drawing the European Union and nearby countries into the dispute, which earlier this month involved a light collision between Turkish and Greek frigates. German Foreign Minister Heiko Maas, who visited Athens ahead of a trip to Ankara, sought to de-escalate tensions but said Germany and the EU stood with member Greece."The current situation in the eastern Mediterranean is equivalent to playing with fire," Maas said after meeting his Greek counterpart Nikos Dendias. "Every little spark can lead to catastrophe."Greece and Turkey vehemently disagree over the extent of their continental shelves. Tensions escalated after Turkey deployed its Oruc Reis survey vessel to disputed waters this month, in a move Athens called illegal.Greece on Monday issued an advisory, known as a Navtex, that it will hold naval exercises in an area off the Greek island of Crete, after Turkey had said on Sunday that Oruc Reis will operate in the same area until Aug. 27. Greece's advisory then prompted a rival Navtex from Turkey that it would also hold drills there on Tuesday.Turkish President Tayyip Erdogan said on Monday that Greece was "sowing chaos" in the Mediterranean, and warned Athens that it would find itself having to face the Turkish navy on its own.After meeting Maas, Dendias said Greece wanted to talk with Turkey but it would not do so "under threats" and Athens stood ready to defend its rights, adding the dispute was an issue for the entire EU and its security.A senior Turkish official said Turkey expected Maas to come with a concrete proposal after talks in Greece, and that Athens did not reciprocate Ankara's willingness to start dialogue."The German visit will surely have positive contributions and results, but it is not realistic to just expect Turkey alone to make concessions," the official, who requested anonymity, said.Germany also intervened last month, prompting Ankara to pause operations for talks with Athens. After Greece and Egypt agreed a maritime demarcation deal, however, Turkey resumed operations.EU foreign ministers are scheduled to meet in Berlin on Aug. 27-28 and will discuss the issue.