(Updates with Macron and Mitsotakis comments throughout)

French President Emmanuel Macron is sending warships to support Greece in the eastern Mediterranean, where Turkey’s bid to claim extensive maritime territory has escalated a regional dispute over energy resources.

Macron’s pledge comes as a boost for Greece, which launched a diplomatic offensive in December to rally support after moves by Turkey that Athens considers a serious challenge to its sovereignty.

Greek President Kyriakos Mitsotakis, whom Macron received in Paris on Wednesday, said the vessels would act as guarantors of peace amid ongoing disputes with Turkey, the Guardian reported.

A Turkish deal signed with Libya’s U.N.-recognised Government of National Accord in November marked out Turkey’s extensive claim to eastern Mediterranean waters that Greece says infringes on its territory around some of its islands, including Rhodes and Crete. The deal also paved the way for the deployment of Turkish troops to back the Tripoli-based government.

Macron condemned Turkey’s involvement in Libya, singling out the deployment of troops and thousands of Syrian rebels to the war-torn country, and the report that two Turkish frigates arrived off the Libyan coast this week.

“These past few days we have seen Turkish warships accompanied by Syrian mercenaries arrive on Libyan soil. This is a serious and explicit infringement of what was agreed upon in Berlin,” the French president said, referring to peace talks held this month that have failed to rein in the fighting.

The French and Greek leaders expressed “near-total agreement on almost every issue,” the Greek Reporter said, with Macron speaking of the countries’ common strategic vision on Europe and the Mediterranean. This signals the possibility of France taking a more prominent role in Greece’s broader disputes with Turkey, which span an area from the Aegean Sea to Cyprus.

This week, Greece rejected a Turkish demand to demilitarise 16 islands in the Aegean, where simmering tensions have led to a sharp rise in aerial dogfights and a number of naval skirmishes near disputed islets in recent years.

At the root of the Greek-Turkish rift is a dispute over the rights to potentially rich hydrocarbon reserves near the island of Cyprus. Turkey believes it has been unfairly shut out of deals signed by regional countries in the eastern Mediterranean, and has opposed attempts by Cyprus and its partners to look for gas, while sending its own drill ships to areas off the island.

The French military has already taken part in joint exercises with Greek forces in Greece and Cyprus, and Mitsotakis hailed France’s military presence in the eastern Mediterranean. Macron said his country stood unequivocally by Greece and Cyprus against what he called Turkish provocations and violations of their sovereign rights.

Turkey on Wednesday hit back at the criticism from Paris, calling on France to end its support for Khalifa Haftar, the general whose Libyan National Army has seized most of the country and driven the Government of National Accord back to areas around Tripoli.

“If France wants to contribute to the implementation of decisions taken at the [Berlin] Conference, it should first stop supporting Haftar,” said Hami Aksoy, the Turkish Foreign Ministry spokesman.