The UN's envoy for Cyprus on Wednesday warned parties in the divided island's peace talks that they had to seize a golden opportunity for reunification.

"The choice now is very much about using this opportunity, or losing it," Espen Barth Eide said after talks in Athens with Greek Foreign Minister Nikos Kotzias.

"We are of course only planning for success, but I think we have to be frank… the inability to solve it this time will not mean that we have another chance in three months… one year or five years, we don't know," the Norwegian said.

Cypriot President Anastasiades and Turkish Cypriot leader Mustafa Akinci are to meet in Geneva from January 9 after negotiations broke down last month.

If all goes well, they will be joined on January 12 by the guarantor powers of Cyprus — Britain, which is the former colonial power, Greece and Turkey.

The envoy said he had a "clear sense" that Turkish President Recep Tayyip Erdogan and Greek Prime Minister Alexis Tsipras would attend, as will new UN Secretary General Antonio Guterres.

Athens last month had hoped to facilitate the talks with a direct meeting between Tsipras and Erdogan, but this prospect now seems less likely.

The five-way talks will be "open-ended" to give negotiators ample time, said Eide, who is special advisor on Cyprus to the UN secretary general.

"We have deliberately not said when it ends… we go there with the ambition of finding a solution, or at least a framework for a solution," Eide said.

"It is not going to be easy… a lot of work has to be done to reconcile the established opening positions," Eide said.

But, he added, "the possibilities are higher than they ever were."

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

The Republic of Cyprus is an internationally-recognised EU member state, while the breakaway Turkish Republic of Northern Cyprus is only recognised by Turkey.

It is hoped the outline of a peace deal can be reached in Geneva after 19 months of UN brokered talks between the rival Cypriot leaders.

Adding the guarantor powers to the mix has only complicated the process, Eide hinted on Wednesday.

"We have the strong feeling that if it was only up to the Cypriots, this problem (would) be solved," he said.

But he stressed that success would send a major signal to a divided Europe and a war-torn Middle East.

The two sides remain far apart on several issues, including how many Greek Cypriots could return to homes they fled in 1974 and future security arrangements.

Eide said security and guarantees were the "key outstanding questions".

"This will be the main focus of the conference next week," he said.

Anastasiades wants all Turkish troops to withdraw but Akinci is determined to keep some on the island.