The United States warned Greek and Turkish Cypriot voters Monday of "serious" and "irreversible" consequences if they reject the U.N. reunification plan in referendums April 24. The State Department said Cypriots should not expect a renewal of peace efforts for a long time if the compromise plan is voted down.

Officials here are not saying that there would never be another attempt at Cyprus peace-making if the plan of U.N. Secretary-General Kofi Annan is voted down. They do say the international community is unlikely to mount such an effort anytime soon, and that any follow-on plan is unlikely to offer Cypriots a better deal than the one before them now.

Greek and Turkish Cypriots go to the polls April 24 for unprecedented twin referendums on the Annan plan, a product of years of diplomatic efforts aimed at ending the 30-year division of the island. Latest polling suggests the plan will win by a broad margin in Turkish northern Cyprus, but its fate is doubtful at best among Greek Cypriots, and it must be approved by both sides to take effect.

The United States has strongly supported Mr. Annan's peace efforts, and at a news briefing, State Department spokesman Richard Boucher said Cypriots should take into account what he said would be "serious, historical and irreversible consequences" if the current opportunity is lost.

"This is the first time the people of Cyprus have had a chance to vote, themselves, on a settlement," he added. "This is the only one on offer. There's no 'Plan B,' there's no alternative diplomatic course, there's no promise that, you know, if this gets voted down, we'll go back the next day and try again. I think everybody's estimate is that there's not a lot of prospects for reaching any other deal, other than this deal."

Cyprus has been divided since 1974, when Turkey occupied the northern third of the island in response to a Greek-Cypriot coup aimed at uniting the island with Greece.

Mr. Boucher said the Annan plan is a compromise in which no party got everything it sought, but which offers clear gains for both. He said it would mean the withdrawal of large numbers of Turkish troops and allow more than 120,000 Greek Cypriots to return to their former homes. He said Turkish Cypriots would also benefit in clear ways, including being able to enter the European Union May 1st as part of a new Cypriot federation.

If either side rejects the plan, only the internationally recognized Greek-Cypriot south would join the EU.

A senior diplomat here dismissed the notion advanced by some Greek Cypriot politicians that a better deal can be had by holding out against the Annan plan. He said any subsequent international effort is unlikely to produce "anything significantly different" and that he doesn't foresee an alternate plan emerging "for a long time in the future."