UN leader Ban Ki-moon will start two days of talks with the rival leaders of divided Cyprus on Monday having warned them that time is running out to seal an accord.

Ban has in the past told Demetris Christofias, head of the internationally recognized Greek-Cypriot government, and Turkish-Cypriot leader Dervis Eroglu, that he could end UN efforts to broker a peace deal.

The two have since redoubled efforts to overcome the legal and political obstacles to rejoining the island split since 1974, diplomats said.

Still far from an accord, they go into the fifth round of talks with Ban at the Greentree Estate in the New York suburbs with a deadline. The Greek Cypriots are due to take over the European Union presidency from January 1 next year which would put all hopes on hold.

"The United Nations is providing all possible support to these Cypriot-led negotiations," said UN spokesman Martin Nesirky ahead of the talks.

"The secretary general looks forward to a productive meeting and concrete progress. He has conveyed his expectations to the leaders for a resolution of this issue. He believes that with political will and firm commitment the two leaders can and should reach a much-needed settlement on Cyprus."

Ban has also spoken of the need for progress in his fifth meeting with the two leaders.

"This will be a more intensive consultation," he told reporters last month. "I believe that time is quite limited."

With Cyprus getting close to the EU presidency, "the window of our opportunity for further progress in negotiations is very much limited. It may be politically difficult and sensitive, when the presidency of the European Union is now going to be part of this."

The United States is also pressing the two sides to overcome their rivalry.

"We urge the leaders to seize this important opportunity to make real and substantial progress toward a settlement reunifying the island as a bi-zonal, bi-communal federation," State Department spokeswoman Victoria Nuland said Saturday.

Ban, who has former Australian foreign minister Alexander Downer as his special envoy, said that if there was a breakthrough an international conference on Cyprus could be the next step in a permanent settlement.

Cyprus has been divided since 1974 when Turkish troops occupied the northern third in response to an Greek-inspired coup in Nicosia aimed at union with Greece. Only Turkey recognizes the Turkish Republic of Northern Cyprus.

The two sides have been faced with growing pressure from the United Nations and European Union to reach an agreement.

The key sticking points have included territorial adjustments, security arrangements and property rights.

New tensions have emerged over the Greek Cypriot government's sale of licenses to search for oil and gas off the coast, which has infuriated Turkey.

However the public is also putting pressure on the two leaders. Inspired by the global "Occupy" movement, youths from across the divide have set up a camp inside the buffer zone that has split the island since 1974, demanding reunification.