PARIS – President Chirac made a last-ditch appeal yesterday for French voters to ratify the European Union’s first constitution, saying the choice is “about your future and that of your children.”

Mr. Chirac warned of dire consequences if Sunday’s referendum produces a French “no” to the treaty – planned as the next big step in a 50-year process of European integration.

“It would open a period of divisions, of doubts, of uncertainties,” he warned in a televised address from the presidential Elysee Palace, his last of a tumultuous campaign. “What a responsibility if France, a founder nation of Europe, took the risk of breaking the union of our continent.”

Mr. Chirac did not address mounting speculation that he will fire his unpopular prime minister if France rejects the landmark treaty. But he urged the French not to turn the plebiscite into a vote of sanction against his administration.

“We must not mistake the question,” Mr. Chirac said. “It is not about saying yes or no to the government. It is about your future, that of your children, of the future of France and the future of Europe.”

Mr. Chirac urged the French not to turn Sunday’s referendum into a vote of sanction against his government. “The decision before us goes far beyond traditional political divisions,” he said.

He said Europeans would regard French rejection “as a no to Europe.”

The president shot down arguments used by opponents, who say the text could be renegotiated to make it more amenable to the French if they vote “no.”

Mr. Chirac dismissed that notion as “an illusion.”

“There is no other project. Europe would be broken down, searching for an impossible consensus,” he said.

Mr. Chirac said a challenge facing Europe is economic competition from America, Japan, China, and “tomorrow India and others.” Europe also must preserve its social model and defend its “values of peace and justice,” he said.

If voters reject the constitution, Mr. Chirac would suffer the humiliation of becoming only the second leader, after General Charles de Gaulle, of losing a referendum since the founding of the French Fifth Republic in 1958.

A “no” could, at least temporarily, kill off the proposed constitution and its stated goal of closer integration among the European Union’s 25 member states. Each state must approve the text by referendum or parliamentary vote for it to take effect in 2006.

Proponents say the constitution, which E.U. leaders signed last October, will streamline E.U. operations and decision-making and give the bloc a president and foreign minister. But French opponents say it will lead to a loss of sovereignty and an influx of cheap labor.

Mr. Chirac has said he won’t resign if the charter is rejected. But government officials said he would likely replace his unpopular right-hand man, Jean-Pierre Raffarin, who in three years as prime minister has overseen a rise in the unemployment rate to 10% and difficult reforms to pensions, health care, and other treasured French social protections.

Interior Minister Dominique de Villepin, who as foreign minister made France’s case at the United Nations against the American-led Iraq war, and Defense Minister Michele Alliot-Marie were seen as the most likely replacements for Mr. Raffarin.

Another possibility is Nicolas Sarkozy, who heads Mr. Chirac’s Union for a Popular Movement and previously, as interior minister, presided over a drop in crime. Mr. Sarkozy is seen as a long shot to replace Mr. Raffarin because of his rivalry with Mr. Chirac.

But Mr. Chirac might name Mr. Sarkozy anyway, some observers say: Handing him the tough job of premier might be the easiest way to dent the popularity of a rival who could challenge Mr. Chirac for the presidency should the French leader stand again in 2007.

The issue is not divided along party lines. Mr. Chirac’s conservatives and the rival Socialists are pushing for a yes, while figures from within both parties are loudly dissenting.

Bucking the party line, a Socialist former prime minister, Laurent Fabius, has campaigned strongly for a no. Yesterday, he warned opponents not to succumb to the belief that they have already won, calling for them to turn out in force on Sunday.

“Everyone is saying this is it, it’s already done,” Mr. Fabius told France-Info radio. “I don’t believe that. It’s not the polls that count, it’s the vote.”

A no would put extreme-right leader Jean-Marie Le Pen on the winning side. The 76-year-old anti-immigration leader has spent his career fighting European integration. He argues that the constitution aims to create a European superstate that would swallow up France.

“France would disappear if we adopted the European Constitution,” the fiery leader told 1,500 people at a rally Wednesday night.

The European Constitution would place France “under the American protectorate of NATO,” Mr. Le Pen claimed.

But even bookmakers had the “no” camp as a hot favorite.

Paddy Power in Ireland and Betfair.com in Britain reported a steady flow of bets for “no” – favored at 1-to-2 odds. “Yes” had slid to 6-to-4.