The UN secretary-general has urged Cyprus' rival leaders as well as Turkey, Greece and Britain to rise to the occasion at a peace summit and seize the chance for a breakthrough deal reunifying the ethnically divided island.
In a statement a day ahead of the summit in Crans-Montana, Switzerland, Antonio Guterres pledged his "steadfast commitment" to supporting negotiations aimed at ending Cyprus' decades-long division and bolstering stability in the turbulent East Mediterranean region.
"The opportunity for the reunification of Cyprus is now finally before us," he said.
"I urge all participants to demonstrate the will and leadership required to conclude a comprehensive settlement."
Mr Guterres echoed his special envoy on Cyprus, who earlier on Tuesday urged the island's leaders to make the most of the summit he called the "best chance" for a breakthrough peace accord.
But envoy Espen Barth Eide said both sides have rejected a UN document intended to structure and steer talks at the summit.
In the absence of such a document, Mr Eide said the onus is on the leaders to chart a course towards a peace deal.
Talks are scheduled until July 7, but may wrap up sooner or take longer depending on developments.
"There will be long days, hard work ahead and make no mistake it's not going to be easy.
"There's no guarantee of success," Mr Eide told a news conference in Geneva.
"It's their conference and they have to take the responsibility and try to make the best out of what I think is a unique opportunity."
Officials have indicated that objections to the document revolved around a reference to how a security structure would be implemented if a deal to reunify Cyprus as a federation is reached.
The summit, which will also include the foreign ministers of Cyprus' "guarantors" Greece, Turkey and Britain, will concentrate on figuring out a mutually acceptable security formula.
An earlier attempt in Geneva in January was unsuccessful.
Other key, unresolved issues, like how much territory will make up each side's federal zone, will be discussed concurrently.
Mr Eide said the UN will not present the document at the talks, but called the effort helpful because it brought clarity to each side's positions on security, which are now "diametrically opposed".
Greek Cypriots want the withdrawal of more than 35,000 troops that Turkey has kept in the island's breakaway Turkish Cypriot north since 1974 when it invaded following a coup by supporters of union with Greece.
They also want military intervention rights accorded by the island's 1960 constitution to the three "guarantors" expunged.
The island's Greek Cypriot president Nicos Anastasiades has proposed an international police force to oversee security backed up by UN Security Council muscle.
Turkey and the minority Turkish Cypriots who see the troops as their sole protection want them to remain under a revised security guarantee system.
Turkish Cypriot leader Mustafa Akinci suggested the Turkish troop presence could be reviewed some 15 years after reunification.
Mr Eide said there are ways to reconcile the opposing positions, since all players involved agree that a peace deal would have positive security repercussions on the island and a conflict-hit region as a whole.
"I think it's the best chance. It's a unique opportunity and it will be extremely sad if it's wasted and I think frankly that's recognised by all participants," he said.