Greece signed a 2.3 billion-euro ($2.8 billion) deal with France on Monday to purchase 18 Rafale fighter jets, as tensions remain high with neighbor Turkey, AP reported.

Florence Parly, the French defense minister, signed the agreement in Athens to deliver 12 used and six new aircraft built by Dassault Aviation over two years, starting in July.

France has sided with Greece in a dispute over boundaries in the Aegean Sea and eastern Mediterranean that has brought NATO members Greece and Turkey to the brink of war several times in recent decades.

Tension spiked again last summer when a Turkish exploration mission in disputed waters triggered a dangerous military buildup.

Greece and Turkey have agreed to restart talks aimed at resolving the dispute peacefully. Senior diplomats from the two countries met in Istanbul on Monday to resume the process that had been interrupted for nearly five years.

But Athens says it will continue a multibillion-euro program to upgrade its military following years of cuts because of the country’s financial crisis.

France and the United States are in competition to provide the Greek navy with new frigates, while Greece’s government recently approved plans to cooperate with Israeli defense electronics firm Elbit Systems to create a new military flight academy in southern Greece.

Parly, who also met Greek Prime Minister Kyriakos Mitsotakis, announced that France would join two Greek military exercises later this year, participating with Rafale jets from the French air force.