The Turkish Cypriot and Greek Cypriot communities are separated by a United Nations buffer zone, and "many attempts to reunite the island have failed", Michele adds. Turkish Cypriots, the minority, see Turkey's military might as their sole insurance against any Greek Cypriot hostility, and want those troops to remain in a final accord.
Flanked by Nicos Anastasiades and Mustafa Akinci, respective leaders of the island's Greek and Turkish Cypriots, Guterres said the reunification talks had "obviously a way to go".
Speaking to journalists in Geneva after the conference, Turkish Foreign Minister Mevlut Cavusoglu said the Cyprus talks had entered a "critical period" but said gaps still remain on "sensitive issues".
The Mediterranean island was divided between Greek and Turkish spheres of influence in 1974, when Turkish troops intervened after a coup meant to unify Cyprus with Greece. Turkey now has 30,000 troops stationed in the northern Turkish part of Cyprus.
Athens said it was in close contact with Anastasiades and Kotzias, who attended in Tsipras's stead.
Former Norwegian foreign minister, Espen Barth Eide is the current UN envoy to Cyprus, and has said the United Nations would only facilitate, and not arbitrate, talks between Greek and Turkish Cypriots, according to Reuters news agency.
Recep Tayyip Erdogan has said it is "out of the question" for Turkey to withdraw its troops from Cyprus, and that Turkey would be on the island "forever", hours after leaders from the divided island said they had made significant progress on attempts at reunification.
UN Secretary-General Antonio Guterres (c) speaks next to Cyprus President Nicos Anastasiades (r) and Turkish Cypriot leader Mustafa Akinci.
While Cyprus has been an European Union member since 2004, Anastasiades's internationally recognised government exercises no control over the northern Turkish-ruled part of the island, and European Union legislation is suspended there until a settlement is reached.
In Geneva, in recent days, they have even broached the one issue they had avoided so far: a system that would guarantee the unified country's independence and security.
Eide said the talks, aimed at creating a bizonal state with some form of shared central administration, were "on track".
Britain and Greece have said they were happy to scrap the deal, but for Turkey it remains a priority. Violence between the two has simmered since 1960, as power sharing has dwindled.
It was the first time security - which has stumped previous rounds of talks - has been discussed at such a high level. "How do we adapt this system through a mutually accepted formula which will secure the security concerns of Turkish Cypriots but at the same time would not cause any threat for the other community?"
"A solution can not create winners and leave losers (in its wake)".
"There is no consensus among sides on when to hold the next Cyprus conference at the ministerial level", Cavusoglu told reporters after an global conference on Cyprus in Geneva.
After that, Anastasiades and Akıncı should be able to iron out the finer details of the deal, draw up a constitution and schedule separate but simultaneous referendums on the two sides in the coming months.