Turkish Cypriot and Greek Cypriot leaders meet at the United Nations Tuesday to try to revive Secretary General Kofi Annan's Cyprus peace plan. Mr. Annan calls the gathering an historic opportunity to reunite Cyprus after three decades of division. But, the path to success is littered with obstacles.

Turkish Cypriot leader Rauf Denktash and his Greek Cypriot counterpart Tassos Papadapoulos come to U.N. headquarters with a deadline hanging over their heads. If they can't settle their 30-year dispute and hold referendums on reunification by April, only the internationally-recognized Greek part of Cyprus will be admitted to the European Union May 1.

The Turkish Cypriot government, which is recognized only by Turkey, would be further isolated.

That prospect has prompted a revival of Secretary General Kofi Annan's Cyprus peace plan, which was shelved last year after three years of wrangling. But even as they agreed to come to New York this week, both Mr. Denktash and Mr. Papadapoulos grumbled publicly about the terms laid down by the Secretary General.

On the eve of the meeting, Mr. Annan acknowledged that a refusal by either side to accept his terms would derail the process.

"Well, if the parties do not agree, and they say no to the plan or the basic agreement, then of course we are back to square one," he said.

And, how does Mr. Annan define square one? "We cannot get agreement," he said.

Mr. Annan said the rival Cypriot leaders have a historic opportunity to unify their country and join the European Union together. He called it a win-win situation.

But he expressed doubt that the two sides have the will to put aside their differences and meet the tight deadlines.

"We don't have much time if we are going to meet the deadline of 1 May. It means we will have to finish the negotiations by end of March to be able to have the referendum in April," he said. "So we will discuss all this to see if the parties are prepared to engage and to sustain the effort for us to ensure that a united Cyprus enters the EU on the first of May."

Cyprus has been split along ethnic lines since 1974, when Turkish troops invaded the northern part of the island. That came after the Cypriot national guard - led by Greek officers - overthrew the government in Nicosia.

The United Nations has maintained a peacekeeping mission along Cyprus's so-called Green Line for nearly 30 years.