Rival Cypriot leaders hold UN-sponsored peace talks in Geneva from Monday billed as a historic opportunity to end decades of division on the island but the outcome is far from certain.

Turkish Cypriot leader Mustafa Akinci and his Greek Cypriot counterpart Nicos Anastasiades have held more than 18 months of negotiations in the run-up to the crunch talks but both men acknowledge that key issues remain to be thrashed out.

The United Nations has pulled out all the stops to get a deal over the line, eyeing the best chance of a settlement in more than a decade.

"It is a real possibility that 2017 will be the year when the Cypriots, themselves, freely decide to turn the page of history," UN envoy Espen Barth Eide said in a New Year's message.

But some analysts believe that Geneva is a disaster waiting to happen because of the deep divisions between the two sides on core issues such as property, territorial adjustments and security.

"I will be surprised if there is a comprehensive agreement given the difficulties," Andreas Theophanous, head of the Cyprus Centre for European and International Affairs, told AFP.

Leaving for the talks on Sunday, the Turkish Cypriot leader told reporters that they marked a "crossroads" and it was vital to "achieve positive results and not just meet up".

"We are not at a point where Geneva will mark the final conclusion. We need to be cautious," Akinci said.

"We are not pessimistic but we shouldn't assume everything is done and dusted. We are expecting a tough week."

- 'Significant differences' -

As he left the island, Anastasiades, who heads the island's internationally recognised government, tweeted that he was heading to the talks "with hope, confidence and unity."

But earlier this week, he too struck a note of caution, warning of "significant differences on substantive issues fundamental to a Cyprus solution".

The island has been divided since 1974, when Turkish troops invaded its northern third in response to an Athens-inspired coup seeking union with Greece.

Nine years later, Turkish Cypriot leaders declared a breakaway state in the north which is recognised only by Ankara.

The years of communal violence, which culminated in the Turkish invasion, saw tens of thousands from both sides flee their homes -- and they remain displaced to this day.

It has always been agreed that some of the territory currently controlled by the Turkish Cypriots will be ceded to Greek Cypriot control in any peace deal.

Just how much and which land they should give up has hampered four decades of peace talks.

The issue is vital because any deal the two leaders reach will have to be put to the vote in their respective communities.

In 2004, a majority of Turkish Cypriots voted in favour of a UN reunification plan but it was overwhelmingly rejected by Greek Cypriots.

The two sides have undertaken to provide maps on Wednesday of their proposals for the internal boundaries of a future bizonal federation.

If that goes to plan, they will be joined from Thursday by the leaders of the island's three guarantor powers -- former colonial ruler Britain, Greece and Turkey.

"I expect neither a success nor a failure but the beginning of a series of final round talks under the participation of the guarantor powers with 'observers' invited from the EU and Security Council," said Hubert Faustmann, professor of history and political science at the University of Nicosia.

Turkish President Recep Tayyip Erdogan and British Prime Minister Theresa May agreed in a phone call on Saturday that the Geneva talks were a "real opportunity" to end the island's division.

But there are differences over future security arrangements with Anastasiades wanting the tens of thousands of Turkish troops on the island to leave but Akinci demanding a continued Turkish military presence.

Akinci also insists on a rotating presidency for the future federation -- a proposal unpopular among Greek Cypriots.

Analyst Theophanous said the most likely outcome of the Geneva talks would be an agreement to continue negotiations in Nicosia.

"It will be an ongoing process but this has been going on for so many years," he said.