U.N. chief Ban Ki-moon will seek a peace deal within a year from Cypriot leaders engaged in reunification talks on Thursday, a source close to the matter said.

Leaders of the estranged Greek and Turkish Cypriot communities have been locked in rounds of negotiations to reunify Cyprus for almost four years.

"It (the process) could not go any slower without stopping altogether. The last three months have been the worst three months we've ever had since these negotiations began in September 2008," U.N. special envoy Alexander Downer told reporters in Geneva, where Ban was due to meet Greek Cypriot leader Demetris Christofias and Turkish Cypriot leader Dervis Eroglu on Thursday.

A source close to consultations told Reuters a deal could be within reach if both sides focused on securing one.

"What we are seeing is too much attention paid to detail and not the bigger picture...They are getting stuck in the weeds," the source said, speaking on condition of anonymity.

Another meeting with the leaders was possible in September, and Ban also could announce he was preparing a report to the Security Council on the state of play in Cyprus negotiations, the source said.

He was expected to seek a commitment from the two that they would ramp up Cyprus-based talks, held in a United Nations compound which forms part of a buffer zone splitting Greek and Turkish Cypriots since a Turkish invasion in 1974 triggered by a brief Greek inspired coup.

The U.N. wants the two sides to adopt a roadmap for progress and resolve outstanding issues in 12 months, concerned that any momentum could fizzle out when Greek Cyprus takes over the rotating presidency of the European Union on July 1 2012.

The Cyprus conundrum weighs on Turkey's bid to join the bloc, in addition to opposition from EU heavyweights France and Germany.

Cyprus is represented in the EU by Greek Cypriots, who nominally represent the whole island, but whose influence is restricted south of a dividing line patrolled by U.N. peacekeepers. Greek Cypriots say Turkey cannot join the union until the Cyprus conflict is resolved.

Mediators are trying to reunify the island as a two-zone federation linked by a strong central government.

Among the most contentious issues are property claims from thousands of internally displaced people, security arrangements and redrawing boundaries between the sides.

Territorial and broader security issues involving the roles of Cyprus's guarantor powers - Britain, Greece and Turkey - have barely been touched in negotiations.

Any agreement the two sides reach must go to referendum. A working assumption is for any deal going to the vote by the end of 2011, or by the first quarter of 2012 at the latest. "A great deal needs to be done to prepare the public for a referendum," another diplomat said.

Reuters