UNITED NATIONS: Greek Cypriot and Turkish Cypriot leaders trying to negotiate an agreement to reunify the divided Mediterranean island must overcome substantial differences during two days of talks starting Sunday.

Secretary-General Ban Ki-moon said after his last meeting with the two leaders in Geneva on July 7 that he expected them to reach agreement by October. But his special adviser Alexander Downer said after the leaders met last week in Nicosia that differences remain.

He refused to discuss the differences, but the two sides reportedly have not agreed on key issues including what to do with private property lost during the war, territorial boundaries, details of a federal government and elections. Cyprus was split into a Greek Cypriot south and a Turkish Cypriot north in 1974 when Turkey invaded after a coup by supporters with Greece.

The island joined the European Union in 2004, but only the internationally recognized south enjoys membership benefits. Numerous U.N.-mediated attempts at reunification have failed, but Ban has been pressing both sides to reach a deal.

Downer said Cypriot President Dimitris Christofias and Turkish Cypriot leader Dervis Eroglu have made progress on several core issues since July 7 "and that's encouraging. But, there are still difficulties to be resolved on the core issues." Downer will join Ban at talks with the two leaders on Sunday and Monday at the secluded Greentree estate in Manhasset, on Long Island, east of New York City.

The secretary-general "wants to hear about what those difficulties are, and to hear from the leaders the sorts of ideas they have for overcoming those difficulties," Downer said. The Greek Cypriots are going into the Long Island meeting with low expectations of any major breakthrough in the three-year-old peace talks.

Christofias said expectations for speedy progress after the July 7 meeting with Ban have not been realized and he accused the Turkish Cypriot side of moving backwards on key issues.

The Turkish Cypriot side is "attempting to portray the situation as if we're close to an agreement," he said after arriving in New York on Saturday. "I also had hoped that we would be close to an agreement, but we're not, and I hope that the Secretary-General is properly informed by his advisers and certainly has the correct assessment of the situation."

"I don't have the greatest and best expectations from this meeting given that the Turkish side is behaving the way it's behaving," said Christofias, urging the Turkish Cypriot side "to change its positions for the better." Christofias has accused Eroglu of backtracking on key aspects of how an envisioned federal state would function, issues that he and Eroglu's predecessor Mehmet Ali Talat had previously agreed on.

The main point of discord according to Greek Cypriots is Eroglu's insistence on a more diluted sovereignty for a future federal government, with more powers flowing to the constituent states. Oppositely, the Turkish Cypriots were heading to Long Island with a more upbeat outlook, saying they expect positive results from the meeting given that the U.N.'s prestige is on the line.

Turkish Cypriots accuse the Greek Cypriots of dithering and lacking the will to push ahead with a deal. Eroglu has said he's going to Long Island "well-prepared."

The talks have made some progress on several secondary issues, including internal security and European Union relations, but wide divergences remain on power-sharing, the fate of mainland Turks who have settled in north Cyprus after the 1974 invasion, arrangements on private property lost in the conflict and the post-settlement boundaries of a Turkish Cypriot-administered north and Greek Cypriot-administered south.

Despite the differences, neither side has even hinted of walking away from the talks, insisting that they're determined to see through the negotiations so as not to be blamed as the spoiler and be burdened with the political consequences of failure.

Downer, the U.N. envoy, has said the world body has invested much in these talks and doesn't want them to end in another failure. The U.N. will gauge in Long Island whether a deal is possible and will likely up the pressure on the leaders, but they may also be weighing their options in case of an impasse.