It is a dispute that has brought NATO partners Greece and Turkey to the brink of war and confounded generations of diplomats; but Geneva negotiations next week offer the best chance in decades of reuniting the ethnically divided island of Cyprus.
On the face of it, the omens are indeed good. Greek Cypriot leader Nicos Anastasiades and breakaway Turkish Cypriot leader Mustafa Akinci are both moderates on an island where emotions are still raw after past intercommunal violence. Discovery of offshore gas fields and a need to secure revenues also should give impetus.
Many Cyprus experts jaded by disappointments over half a century are sceptical, if open to being surprised. Even if a settlement hove into view, the tight deadline is unrealistic.
“Anything can happen,” said political analyst Hubert Faustman. “They hope to make progress on as many issues as possible but there may be a need for other meetings because they have left so many outstanding issues till the last moment.
“I don't see them spectacularly failing, that is a possibility, but unlikely, because nobody wants to lose the blame game,” he told Reuters.
If all goes according to plan, the talks will culminate in an exchange of maps on January 11 defining future boundaries in a united federal system comprised of two states.
Representatives of Britain, Turkey and Greece - the guarantor powers of the former British colony - will discuss their roles at a conference starting in Geneva the next day.
But that would leave negotiators still far from a settlement for an east Miditerranean island split into separate zones since Turkish troops invaded in 1974 in response to a short-lived coup by Greek Cupriot militants seeking union with Greece.
Resolving the status of those security 'guarantees' is a central issue and a source of long-standing mutual mistrust.
“I am not sure the sides will be ready to make the compromises this time in Geneva,” Ahmet Sozen, a Turkish Cypriot academic who has researched extensively on the subject, told Reuters.
“I truly hope so, but the signs we are getting so far are not very encouraging. But I don't know, especially at such conferences where there is high level participation.. things can change.”
Under a 1960 treaty, Britain, Turkey and Greece can intervene in Cyprus in the event of a breakdown of constitutional order.
Publicly, the views of the two sides are diametrically opposed. Fearful of a repeat of the 1974 Turkish invasion, the Greek Cypriots see such guarantees as undesirable. Turkish Cypriots, who withdrew into scattered enclaves in the violence of the 1960s and were targeted by Greek Cypriot nationalists, say they need a system of protection.
About 30,000 Turkish troops are stationed in breakaway northern Cyprus, a Turkish Cypriot state backed financially and politically by Turkey, the only country to recognise it. The south is run by a government which represents the whole island in the European Union.
“Cyprus is one of the few areas to offer tremendous hope in 2017,” said Espen Barth Eide, a UN envoy facilitating the process.
Turkish Foreign Minister Mevlut Cavuslogu was equally upbeat. “I am more optimistic than ever...It is not easy but we are determined about reaching a solution,” he was quoted as telling Anatolian news agency.
Should the sides come up with a peace blueprint, several more weeks would be required to write a constitution that will among other things set out the powers of the two federal states.
But like everything in the Cyprus conundrum, nothing is agreed until everything is agreed.
A previous peace bid collapsed in 2004, when Turkish Cypriots accepted but Greek Cypriots rejected a blueprint.
“We are heading to the end-game, but we are not there yet,” said a senior EU official.