In separate telephone calls yesterday with Greek Cypriot leader Demetris Christofias and Turkish Cypriot leader Dervis Eroglu, Mr. Ban also encouraged both men to redouble their efforts in the months ahead towards reaching a mutually acceptable solution.The talks, launched in 2008, seek to set up a federal government with a single international personality in a bi-zonal, bi-communal country, with a Turkish Cypriot constituent state and a Greek Cypriot constituent state of equal status.The Secretary-General noted that there had been some convergences, particularly in the chapters on economy and on European Union matters. However, he said, there has been no significant progress in the other chapters, according to information released by his spokesperson.In addition to economy and EU matters, the core issues in the negotiations include governance and power-sharing, property, territory and security. In a report in December, Mr. Ban warned that that the talks could “founder fatally” if substantive agreement is not reached within the next few months. “A critical window of opportunity is rapidly closing,” he said, stressing that Greek Cypriot parliamentary elections scheduled for May and elections in Turkey in June militate against constructive talks in the second quarter of 2011. The Secretary-General met with both leaders in Geneva at the end of January, and the two agreed to intensify the talks to reunify an island that has been split since inter-communal violence erupted in 1964. The UN has maintained a peacekeeping force on the island – known by its acronym UNFICYP – since 1964, with a current strength of nearly 1,000 uniformed personnel and 150 international and national civilian staff. 4 April 2011Secretary-General Ban Ki-moon has proposed holding a meeting with the Greek Cypriot and Turkish Cypriot leaders in mid-June to review developments in the United Nations-backed negotiations aimed at reunifying the Mediterranean island.