GENEVA -- A summit meeting between the rival leaders of ethnically divided Cyprus in this Swiss city will determine whether the east Mediterranean island nation can finally be reunified after decades of failed attempts and dashed hopes, a U.N. envoy said Monday.

Espen Barth Eide said that 19 months of difficult and complicated talks between Greek Cypriot President Nicos Anastasiades and breakaway Turkish Cypriot leader Mustafa Akinci have reached their "moment of truth" and that the next few days would decide if a peace deal can be achieved.

"We are now in the final moment," Eide told a news conference at the start of the weeklong summit. "We are now really at the moment of truth. This is where we will actually find out if this can be solved."

Anastasiades and Akinci kicked off the summit with talks on how much territory each side will control in an aimed-for federation and how people who lost homes and property when the island was split along ethnic lines 43 years ago will be able to reclaim them.

A 1974 Turkish invasion triggered by a coup aimed at uniting the island with Greece divided the island into a Turkish speaking north and a Greek speaking south. Only Turkey recognizes a Turkish Cypriot declaration of independence and keeps more than 35,000 troops in the north.

The two leaders have three days to reach agreement on these and other outstanding issues before the summit takes an international dimension, when the island's so-called guarantors -- Greece, Turkey and former colonial overseer Britain -- tackle the difficult issue of post-settlement security arrangements.

Eide said that it's up to Anastasiades and Akinci to hammer out a deal and that the U.N. won't arbitrate. The U.N. envoy underscored the talks' "Cypriot ownership" in order to avoid a reprise of a 2004 U.N. brokered deal that three-quarters of Greek Cypriots rejected in a referendum as unfairly weighted against them.

"It's the leaders in Cyprus that are responsible for every single sentence, every single word in the talks, there is no kind of U.N. arbitration and there will not be," Eide said.

The U.N. envoy conceded that talks have been "stuck" on some points regarding how owners will reclaim lost property, but insisted that there is no issue that can't be resolved "if sufficient will is available."

Talks on security dubbed as the "Conference on Cyprus" start Thursday and a key question is how high-level they will be.

Officials at the European Union -- of which Cyprus is a member -- said that European Commission President Jean-Claude Juncker and the EU foreign policy chief, Federica Mogherini, planned to attend. That pointed to the importance of the stakes for the 28-member bloc.

It's still not certain who will represent Greece, Turkey or Britain at the conference. Eide said the three guarantors will be represented at the "highest or second-highest level," noting that the effectiveness of the conference will depend on how much progress the two leaders make in the preceding three days.

Eide said that a Cyprus deal wouldn't only be "historic" for Cyprus, it would send a "very strong signal" to a strife-torn region.

Menelaos Hadjicostis reported from Nicosia, Cyprus