NICOSIA, Cyprus — The latest round of talks in a decades-long effort to reunify the ethnically split island nation of Cyprus collapsed on Friday.

While many issues remained unresolved, the deal breaker was a clash over what would happen to the more than 35,000 troops that Turkey has kept in the island’s breakaway Turkish Cypriot north since 1974, when it invaded after a coup mounted by supporters of union with Greece.

“Now our voices need to be louder, more convincing,” said an activist, Tina Adamidou, who has participated in nightly peace demonstrations at the United Nations-controlled buffer zone that cuts across the country’s capital. “We need to show that as Cypriots we are united.”

Greek and Greek Cypriot officials said it was Turkey’s “obsession” with keeping its troops in place and the right to militarily intervene post-reunification that derailed the talks. Turkish and Turkish Cypriot officials said pulling all troops out and abolishing intervention rights were out of the question.