Germany holds the rotating European Union presidency and before departing Berlin, Foreign Minister Heiko Maas said Greece and Cyprus had both German and EU backing but urged an "honest effort on all sides" to find a solution.

Greece on Monday accused neighbour Turkey of undermining efforts to ease a crisis over eastern Mediterranean drilling rights, after Ankara redeployed a survey vessel for new energy exploration in disputed waters — including an area very close to a secluded Greek island. The move reignited tensions over sea boundaries between Greek islands, Cyprus and Turkey's southern coast, which had flared up over the summer, prompting a military build-up, bellicose rhetoric and fears of a confrontation between the two NATO members and historic regional rivals. The Turkish search vessel, Oruc Reis, left the port of Antalya on Monday for a mission expected to end October 22.

Maas stressed that talks between the nations can only work in a "constructive atmosphere" and appealed "to Turkey not to close the window for dialogue that has just opened with Greece through unilateral measures." "Ankara must stop alternating between relaxation and provocation if the government is interested in talks, as it has repeatedly said," he said. Renewed Turkish gas exploration in the disputed areas would be "a major setback to efforts to de-escalate and thus also for the further development of EU-Turkey relations," Maas said