UNITED NATIONS — The United Nations secretary-general promised Sunday to lend his personal support to rival Cypriot leaders who are locked in complex talks aimed at reunifying the ethnically divided island nation.

Ban Ki-moon said he and the U.N. will personally do “our utmost” to assist Greek Cypriot President Nicos Anastasiades and breakaway Turkish Cypriot leader Mustafa Akinci resolve the decades-old problem.

Ban, who met with both leaders Sunday, called on them to “make the most” of the time ahead to overcome hurdles still impeding an accord. A key obstacle that’s complicating negotiations is a Turkish Cypriot demand for Turkey to retain military intervention rights on the island. Greek Cypriots say intervention rights have no place in an envisioned federated Cyprus and insist this would scotch any agreement.

Ban said he stands ready to help the two sides on whatever they require, including the “international dimensions” of the issue — an indirect reference to intervention rights that were ceded to Greece, Turkey and Britain under the constitution of Cyprus that gained independence from British rule in 1960.

Cyprus was divided into a Turkish speaking north and a Greek speaking south in 1974 when Turkey invaded after a coup that aimed to unite the island with Greece. Only Turkey recognizes a Turkish Cypriot declaration of independence. Although the island joined the European Union in 2004, only the internationally recognized, southern part enjoys full membership benefits.

The island’s division is a major impediment to Turkey’s EU membership bid and complicates energy cooperation on offshore gas deposits in the east Mediterranean.

“The period ahead will be crucial for Cyprus,” Ban said after the meeting. “Time is of the essence.”

Both Anastasiades and Akinci have said they aimed to reach a deal by year’s end. Anastasiades said Sunday the target for a 2016 deal still stands, although he called it “ambitious.”

Anastasiades said no deadlines, timeframes or third-party arbitration were imposed on negotiations during the meeting with Ban. Greek Cypriots fear any outside pressure may unfairly tilt the terms of any agreement.

Anastasiades said negotiations would be stepped up when he and Akinci return to the island.

Akinci said he told Ban that talks should take on a new “format” where key aspects of a deal — including how much territory would be administered by either side would be hammered out.

He also pointed to what he called risks of allowing talks to drag on beyond the end of the year. Presidential elections in the south are slated for February, 2018.

Associated Press writer Menelaos Hadjicostis contributed from Nicosia.