Greek Cypriot leader Glafcos Clerides has flown to Copenhagen ahead of the European summit on enlargement, but with little optimism of an imminent breakthrough towards a peace deal.

The Turkish Cypriot leader, Rauf Denktash, has said that he will not sign a United Nations plan for the reunification of Cyprus at the summit which begins on Thursday.

It would be easy to reject the plan as some hotheads are suggesting Glafcos Clerides

In an interview with a Turkish television channel, he said he needed more time to be able to discuss it with the Greek Cypriot side, but said the document contained what he called "certain improvements".

Diplomats have been hoping for a last-minute deal which enable both sides of a united Cyprus to join the EU together.

"It would be easy to reject the plan as some hotheads are suggesting," Mr Clerides said as he left for Copenhagen.

"But I must give very serious thought to it."

The UN has been pressing hard for a peace deal so that Cyprus' entry to the European Union - due to be approved at the summit - is completed in its post-settlement form.

But UK Foreign Secretary Jack Straw said on Wednesday he was not optimistic that a deal would be reached in Copenhagen.

"The signs are not hopeful - there are difficulties," he said.

He said that he was simply hoping for "further progress".

Mr Denktash, who recently underwent heart surgery in New York and is travelling to Turkey for further treatment, may send a representative to Copenhagen.

The UN insists that Mr Denktash's absence need not halt the peace process.

The UN "has no objection to dealing with anyone that Mr Denktash or his delegation might designate to negotiate on his behalf," spokesman Fred Eckhard said.

"Anyone who is delegated by the Turkish Cypriot side can sign as far as we are concerned," he said.

'Historic' opportunity

UN Secretary-General Kofi Annan has told the two sides they have a "rendez-vous with history" in Copenhagen, urging them not to let the opportunity pass.

The EU has said it will accept Cyprus even if reunification has not been agreed - a move which Turkey has said it would meet by annexing the northern part of the island.

The UN's peace plan suggests a Swiss-style confederation of two equal states. Cyprus has been divided since 1974, when Turkish troops invaded after a short-lived Greek-inspired coup.

Turkish Cypriots still run their self-declared republic in the north, but only Turkey recognises its existence.