NICOSIA, Cyprus -- Progress has been slow in high-level talks to reunify the ethnically divided Mediterranean island nation of Cyprus, U.N. Secretary-General Antonio Guterres said Friday, with security issues in particular standing in the way of a peace accord.

The U.N. chief, whose presence on the third day of talks at the Swiss resort of Crans-Montana is intended to give the talks a boost, also played down suggestions that the body is getting weary of the drawn-out problem, which has been in its in-tray since 1964.

"There is still a lot of work to be done," Guterres told reporters after lunch with the east Mediterranean island's Greek Cypriot President Nicos Anastasiades and the leader of the breakaway Turkish Cypriots, Mustafa Akinci.

"It is slow progress and many outstanding issues are still to be resolved."

Guterres said "new positions showing increased flexibility" in some issues had been relayed and that some gaps between the rival sides have narrowed.

"We're not impatient and we're not threatening the parties in any way," said Guterres, adding that putting a deadline on talks would invite collapse of the process.

Also at the talks were top diplomats from Cyprus' so-called "guarantors" -- Greece, Turkey and Britain.

Anastasiades said morning talks chaired by Guterres offered possible ways out of deadlock. Greek Foreign Minister Nikos Kotzias echoed Anastasiades, calling the U.N. chief's input "useful and beneficial."

Central to negotiations are opposing views over the island's future security -- agreement on that issue has the potential of unlocking an overall peace accord.

Turkey is rebuffing Greek and Greek Cypriot calls to remove all troops from breakaway northern Cyprus after the island is reunified as a federation. It insists that any peace accord should grant Turkish citizens the right to relocate and transfer money, services and goods to the European Union member island.

Although Cyprus joined the EU in 2004, only the Greek Cypriot southern part that is the seat of the island's internationally recognized government enjoys full benefits.

The island was split in 1974 when Turkey invaded following a coup staged by supporters of union with Greece. Turkey has since stationed more than 35,000 troops in the north.

Turkey and the minority Turkish Cypriots want at least some of the troops to remain and enforce the peace after reunification under revised military rights accorded to the guarantor nations under Cyprus' 1960's constitution.

Greece and the Greek Cypriots want military rights abolished and all Turkish troops removed, replaced instead by a U.N. Security Council-backed international police force.

"We won't allow anyone to ask for all or nothing," Kotzias said before the start of talks Friday.

Turkish Foreign Minister Mevlut Cavusoglu on Thursday scolded Greece and Greek Cypriots to "wake up from their dream" that Turkey will withdraw all of its troops from Cyprus and give up military rights there as part of any agreement.

Other unresolved core issues including a Turkish Cypriot demand to hold the island's future federal presidency on a rotational basis are being discussed concurrently. But movement on those matters hinges on overcoming the security hurdle, officials said.