The United Nations failed on Thursday to bridge disagreements over restarting peace talks on ethnically-split Cyprus, with the rival sides standing their ground in a conflict that spans half a century.

Diplomats had been trying to break a jogjam in talks between rival Greek and Turkish Cypriots, which collapsed in acrimony in 2017. Cyprus’s split is a constant source of tension between NATO allies Greece and Turkey, and has taken on sharper focus since the discovery of natural gas in the region.

“The truth is that at the end of our efforts, we have not yet found enough common ground to allow for the resumption of formal negotiations,” U.N. Secretary-General Antonio Guterres told a news conference in Geneva after a three-day summit.

“As you can imagine, this was not an easy meeting,” he said.

Cyprus was split in two in a Turkish invasion in 1974 triggered by a brief Greek-inspired coup. The seeds of division had been sown earlier, when a power-sharing administration of Greek and Turkish Cypriots crumbled amid violence, just three years after independence from Britain in 1960.

For decades, the United Nations has been attempting to piece Cyprus back together as a two-zone federation – the only thing the two sides had, until recently, been able to agree to in principle.

TWO-STATE SOLUTION

Under a new leadership, Turkish Cypriots now say only a two-state solution can work.

“Nobody should expect us to be patched onto a unitary, single state. We are negotiating for a two-state solution,” Turkish Cypriot leader Ersin Tatar said. Only Turkey recognizes the breakaway state Tatar leads in Northern Cyprus.

A two-state deal would imply recognition of the Turkish Republic of Northern Cyprus (TRNC), something Greek Cypriots who nominally run the whole island say is out of the question.

Nicos Anastasiades, the Greek Cypriot leader who leads a government recognized internationally and within the European Union as representing the whole island, said Guterres had told the Turkish Cypriots he could not deviate from his U.N. mandate.

“He (Guterres) made it clear that he could not seek recourse, as was requested by the Turkish Cypriot and Turkish side, to the (United Nations) Security Council for a change to terms of reference,” Anastasiades said, adding there was “not a single chance” of switching the basis of talks.

The talks were attended by the foreign ministers of Britain, Turkey and Greece, who are guarantor powers for Cyprus and still maintain intervention rights to restore any constitutional breakdown.

Turkish Foreign Minister Mevlut Cavusoglu said the Greek Cypriot side had brought no new proposals to Geneva and had sounded “like a broken record”.

Guterres said the United Nations would make a fresh attempt in “probably two or three months”.

“Unfortunately today we are not able to reach the agreements that we would wish to reach, but we are not going to give up,” he said.