The rival leaders of Cyprus have once again failed in a meeting brokered by the United Nations (UN) to revive a peace process to reunify the ethnically-divided eastern Mediterranean island.

Greek Cypriot leader Nicos Anastasiades met with his Turkish Cypriot counterpart Mustafa Akinci in the UN-controlled buffer zone in Nicosia on Monday in yet another attempt to end 43 years of ethnic division in Cyprus.

After the talks, Anastasiades told reporters that the discussions covered all the differences between the two sides but both sides “remain in their positions.” He did not, however, exclude the possibility of the UN sending an envoy to Cyprus to examine a resumption of talks.

The UN said in a statement that the two leaders “had a frank and open exchange of views” in the one-on-one meeting.

The island has been divided into Turkish Cypriot-controlled northern and Greek Cypriot-controlled southern territories since a brief war in 1974, which saw Turkey intervene militarily in response to a military coup on the island, which was backed by the Athens government to annex Cyprus to Greece.

Greek Cypriots run the island’s internationally recognized government, while Turkish Cypriots have a breakaway state in the north — only recognized by Turkey — and say offshore resources belong to them, too.

The Greek Cypriot leader has said the reunification talks cannot resume as long as Turkey blocks foreign companies from drilling for oil and gas off Cyprus. He has accused Ankara of practicing “gunboat diplomacy.”

Last month, the European Union condemned Turkey for preventing the Greek Cypriot government from exploring for oil and gas.

Turkey, which does not have diplomatic relations with the Greek Cyprus, has vowed to prevent what it sees as a unilateral move by Greek Cypriots to claim offshore resources. It says some areas of Cyprus’s offshore maritime zone fall under what Ankara calls the territory of the Turkish Cyprus.

The last high-level talks for reunifying the island as a bi-zonal, bi-communal federation collapsed last July. Failures in previous talks have increased tensions between Greece and Turkey — NATO allies, who have been at odds over the divided island.