NICOSIA - The Turkish Cypriot leader on Wednesday warned talks to reunify the island were being undermined by a move from Greek Cypriots to mark in schools a 1950 referendum on unifying the island with Greece.
The Republic of Cyprus and breakaway Turkish Cypriot north have in recent weeks engaged in a fragile UN-backed process to reunify the island.
But Turkish Cypriot leader Mustafa Akinci warned that the talks were being endangered by the approval by the Republic of Cyprus parliament to mark the 1950 plebescite in schools.
The 1950 referendum -- before Cyprus won independence from colonial ruler Britain -- overwhelmingly approved "Enosis" (union) with Greece but had no legal value.
In a letter to UN Secretary General Antonio Guterres, Akinci warned that the move would cause "great damage" to the peace process.
With new talks coming in March, he said it was "not compatible" with UN calls for the parties to take confidence-building steps for a solution.
The Greek Cypriots should "refrain from further complicating such a challenging job for a viable and long lasting solution through such steps," he was quoted as saying.
In later comments, he added: "We will, or won't we, continue to work together for a solution for this island? This is now a very critical question."
Turkey's foreign ministry warned that the issue showed how difficult it would be to reunify Cyprus.
"As long as a fundamental change does not take place in such a Greek Cypriot mentality... it will be difficult to achieve results from efforts aiming towards a settlement in Cyprus."
The bill, sponsored by the far-right ELAM party, essentially calls for secondary school pupils to mark the referendum anniversary by learning about the event and reading leaflets dedicated to understanding the Enosis cause.
The eastern Mediterranean island has been divided since 1974, when Turkish troops invaded in response to an Athens-inspired coup seeking union with Greece.
Akinci, born in Limassol which is now in the Greek Cypriot south, has been an outspoken proponent of a deal along with his Greek Cypriot counterpart Nicos Anastasiades.
UN Cyprus envoy Espen Barth Eide met both leaders separately in a bid to defuse the row after Akinci cancelled their meeting on Tuesday.
"This is not the best climate," Eide admitted in Nicosia after the talks. The two leaders are due to meet for crucial face-to-face talks on Thursday.