Geneva - UN chief Antonio Guterres led a crunch conference on Thursday aimed at ending decades of division in Cyprus, billed as the "very last chance" to solve one of the world's longest-running political crises.Guterres was undertaking his first foreign trip as the United Nations' new secretary general in a bid to achieve a breakthrough at a Geneva summit that involves rival Cypriot sides as well as Greece, Turkey and former colonial power Britain.The eastern Mediterranean island has been divided since 1974, when Turkish troops invaded in response to an Athens-inspired coup seeking union with Greece. Thursday's multi-party talks follow three days of negotiations between Greek Cypriot President Nicos Anastasiades and Turkish Cypriot leader Mustafa Akinci aiming to forge a united, two-zone federation. The intra-Cypriot talks have focused on thorny domestic issues such as territory and what a future, unified government might look like. UN Cyprus envoy Espen Barth Eide has called this week "the moment of truth" and insisted that a deal to solve the long-standing division was within reach.Guarantor powers Guterres, in office since January 1, was hosting top diplomats from Cyprus's so-called "guarantor powers", including British Foreign Secretary Boris Johnson, and his counterparts Nikos Kotzias of Greece and Turkey's Mevlut Cavusoglu.Under a 1959 treaty, those nations were allowed to intervene to defend the island's sovereign integrity, which Ankara used to justify its invasion.Any peace deal will likely include significant changes to or even the elimination of the guarantor power arrangement.Greece has called it out of date and Britain has said it was happy to give it up if Cypriots asked, but Turkey on Thursday insisted that some form of the system needed to be preserved. "Taking into consideration the current situation in our region, continuation of the Security and Guarantees system... is a necessity," Cavusoglu told the closed-door conference, according to a speech released from his office. Britain also retains military bases in Cyprus that are sovereign British territory but has offered to give up nearly half of its land as part of a final settlement. The estimated 30 000 Turkish troops deployed on the island remain a deeply divisive issue, with Anastasiades wanting them to leave the island but Akinci determined to keep a military presence.UN peacekeepers also safeguard a buffer zone between the two sides.This photo taken from the Greek Cypriot controlled area in the south, shows a Turkish military guard post at the Turkish Cypriot breakaway northern part of the divided capital Nicosia in the eastern Mediterranean island of Cyprus. (Petros Karadjias, AP) 'Very last chance' In a crucial step, Anastasiades and Akinci late Wednesday exchanged maps detailing their visions of how internal boundaries should be redrawn.Turkish Cypriot leaders have agreed in principle to return some of the land they have controlled since the failed 1974 coup.Greek Cypriot government spokesperson Nikos Christodoulides said that the presented map was "within the framework" agreed during previous negotiations that foresees the Turkish Cypriot zone amounting to a maximum of 29.2% of the island. "We consider it as a particularly positive development," Christodoulides said while noting that disputes remain and a final map has not been agreed. On Tuesday the two sides tackled the island's relations with the European Union, with the UN seeking to create a unified nation that would be a full EU member. While Cyprus has been an EU member state since 2004, Anastasiades's internationally recognised government exercises no control over the northern Turkish-ruled part of the island, and EU legislation is suspended there until a settlement is reached.European Commission president Jean-Claude Juncker, in Geneva as an observer to the conference, said before arriving that the island's future was hanging in the balance. "I really think that, without overdramatising what is happening in Geneva, this is the very last chance to see (a solution for) the island being imposed in a normal way," he said.