The European Union on Thursday appealed to Greek and Turkish Cypriot leaders to persuade voters on the divided island of Cyprus to accept a U.N. reunification plan in upcoming referendums.

Secretary-General Kofi Annan's plan is a last-ditch attempt to reunify the Mediterranean island before it joins the EU on May 1. The two sides and the Greek and Turkish governments failed on Wednesday to reach an agreement of their own after lengthy talks.

Guenter Verheugen (search), who represented the EU at the reunification talks in Switzerland, said the deal was "the best and most balanced solution that can possibly be achieved" to allow a unified Cyprus to join nine other countries in a historic expansion of the bloc.

Annan ordered parallel referendums April 24 in both the Greek and Turkish parts of the island for voters to decide whether to accept his blueprint.

"There have been too many missed opportunities in the past. For the sake of all of you, I urge you not to make the same mistake again," Annan said Wednesday on the final day of peace talks in the Swiss mountaintop resort of Buergenstock (search).

If either side rejects the plan, only the Greek part of the island will join the EU on May 1 and the breakaway state in the Turkish-occupied north of the island will be deprived of EU benefits.

"The alternative is this plan or nothing, no solution at all," Verheugen, the EU expansion commissioner, told the European Parliament in Strasbourg, France.

"There can be no changes to this plan," he said. "That has to be made perfectly clear."

Cyprus has been split into the Greek Cypriot-controlled south and the occupied north since Turkey invaded in 1974 following a short-lived coup by supporters of union with Greece. The breakaway state is only recognized by Turkey, which maintains 40,000 troops there.

The plan — 220 pages long and with about 9,000 pages of annexes — envisages separate Greek and Turkish Cypriot states linked by a weak federal government.

"We have now reached a stage where we need strong political leadership," Verheugen said. "And here I would call on the Greek and Turkish Cypriot leaders to do all they can to try and persuade the population of the island that the present plan represents the best and most balanced solution."

Turkey's government, which is keen to see a settlement in Cyprus as a step toward eventually joining the EU itself, quickly endorsed the proposal.

"No side has lost in these negotiations," Turkish Prime Minister Recep Tayyip Erdogan (search) told reporters on Wednesday.

He said the most important issues for Turkey were ensuring that the agreement would be adopted by the European Union, political equality for the Turkish Cypriot minority, boosting prosperity in the impoverished north, ensuring the continued presence of Turkish troops and protecting some 80,000 Turkish settlers.

The Greek side was more cautious after expressing disappointment in the failure to guarantee Turkish troop withdrawal and the return of all Greek Cypriot refugees to their homes in the northern part of the island.

"Unfortunately it was not possible to reach an agreed settlement. It is now up to the people of Cyprus to reach a decision and I hope they will do this with clear thought and vision," Greek Prime Minister Costas Caramanlis said.

In Berlin, U.S. Secretary of State Colin Powell said the settlement proposed by Annan was fair to both sides and he urged Greek and Turkish Cypriot voters to approve the proposal.

"We know they will make this choice with the future of all Cypriots in mind," Powell said in a statement.

According to the plan, a proportion of the Greek Cypriot refugees who fled or were forced from their homes in the north will have the right to go back. Turkey must drastically reduce — but not withdraw entirely — the number of troops it maintains on the island.

The United Nations has been in Cyprus since 1964 and maintains more than 1,200 peacekeepers there. Successive secretaries-general have tried to solve the Cyprus problem but have been unable to find a solution that satisfied both communities.

Annan's most difficult task will be convincing the Greek Cypriot majority to vote for the plan.

The Greek Cypriot majority knows that — whatever the outcome of the vote — they will join the European Union on May 1 and get all the benefits that entails. Their standard of living is five times that of the Turkish Cypriots (search), and reunification would require them to pour money into the impoverished north.

Yet the Greek Cypriots (search) have deep emotional reasons for wanting to see their island reunited. Some 180,000 people are waiting for the chance to return to their homes in the north.

Despite the restrictions, Verheugen said Annan's plan satisfied the European Union's condition that any reunification formula respect EU rules on freedom of movement because they were not permanent.