Updated

A summit aiming to reach a breakthrough agreement reunifying the ethnically divided Mediterranean island nation of Cyprus will be held on June 28 in Geneva, Switzerland, a spokesman for the U.N. Secretary-General Antonio Guterres said Friday.

Spokesman Stephane Dujarric said the meeting, under the auspices of Guterres, will bring together the Greek and Turkish Cypriot leaders and officials from Cyprus' "guarantor powers" — Greece, Turkey and Britain.

Dujarric said the European Union will be present as an observer.

Cyprus was split into a breakaway Turkish Cypriot north and an internationally recognized south in 1974 when Turkey invaded following a coup by supporters of union with Greece. Only the south enjoys membership rights in the U.N. and E.U.

The summit is seen as a culmination of two years of negotiations between the island's Greek Cypriot President Nicos Anastasiades and Turkish Cypriot leader Mustafa Akinci, who have made significant headway toward an accord reunifying Cyprus as a federation.

But disagreements on core elements remain, including how post-reunification security will be handled and how much territory will make up the Greek and Turkish Cypriot federal zones.

The summit will focus on overcoming these issues before an agreement can be put to a simultaneous vote for approval by both communities.

Anastasiades insists on prioritizing agreement on the withdrawal of over 35,000 troops that Turkey keeps in the north and which Greek Cypriots see as a threat. Turkish Cypriots see the troops as their sole security guarantee and want to keep them in place. Turkish officials have said there can be no peace deal without at least some degree of a Turkish military presence on the island.

U.N. envoy Espen Barth Eide, who has helped mediate the talks, said the summit is formally open-ended, but likely to last two weeks. That would put its conclusion just before French energy company Total begins exploratory oil and gas drilling off Cyprus' southern coast which Turkey and the Turkish Cypriots oppose amid arguments that the "unilateral" Greek Cypriot action flouts their rights to the island's mineral wealth.

Turkish officials and Akinci have warned of a possible crisis if drilling goes ahead without a peace deal. The Cypriot government says drilling is its sovereign right and won't be suspended, while any hydrocarbons proceeds will be shared after a peace deal.