By CHRISTOPHER MARQUIS
 
ASHINGTON, Feb. 25 — France called Wednesday for the immediate formation of a United Nations-backed security force to go to Haiti and stabilize the country, which is in the third week of a rebel uprising. It also urged President Jean-Bertrand Aristide to resign.

The proposal, which was outlined by Foreign Minister Dominique de Villepin and will be presented Thursday to United Nations diplomats, could result in the deployment "within days" of a multinational police force, a French diplomat said.

But the proposal was ambiguous about whether Paris would support dispatching the force without first obtaining an agreement between the Haitian political opponents and Mr. Aristide's government.

A senior State Department official said talks with the French had suggested that they did not want to intervene in a hostile environment. The crisis has linked the interests of Haiti's nonviolent opposition to armed rebels who have set their sights on the capital, Port-au-Prince. [Page A3.]

The French proposal also calls for the voluntary departure of President Aristide as part of a settlement. Mr. Aristide, who became Haiti's first elected president in 1990, has said he will not step down until his second term runs out, in 2006.

But France, which surrendered its colonial power in Haiti two centuries ago but left a strong cultural imprint, now contends that the Aristide government has lost its legitimacy and should be replaced.

"The regime has reached an impasse and has already shaken off constitutional legality," Mr. de Villepin said.

As turmoil mounted in Haiti, President Bush issued a stern warning to Haitians that the United States would not tolerate a refugee influx to Florida. American patrols will continue to intercept and send back any Haitians trying to escape to the United States by boat, he said.

"I have made it abundantly clear to the Coast Guard that we will turn back any refugee that attempts to reach our shore, and that message needs to be very clear, as well, to the Haitian people," Mr. Bush said, in his most extensive remarks on the crisis. "We will have a robust presence with an effective strategy, and so we encourage, strongly encourage, the Haitian people to stay home as we work to reach a peaceful solution to this problem."

The Coast Guard intercepted a Panamanian-registered ship Wednesday about seven miles off Miami, but did not confirm television reports that it might have been hijacked by Haitians, Reuters reported.

Administration officials said they welcomed the French proposal, but would need to study it before commenting. Secretary of State Colin L. Powell has been in close contact with Mr. de Villepin, speaking with him twice on Wednesday, suggesting that their positions may not be far apart, an official said.

France has security forces in the Caribbean that could be deployed quickly as peacekeepers, probably with others from the region, a French official said. The Bush administration has so far not envisioned sending American forces; it would most likely provide logistical and financial support.

Mr. de Villepin's proposal recommends "the immediate establishment of a civilian peacekeeping force," but it is unclear whether the force would impose a peace accord or protect one after it is reached. French diplomats said the ambiguities would be addressed Thursday.

"This international force would be responsible for guaranteeing the return to public order and supporting the international community's action on the ground," the proposal said. "It would come to the support of a government of national unity."

The proposal incorporates elements from a plan presented by the United States and the Caribbean Community, or Caricom, to Mr. Aristide and his opponents last weekend. Mr. Aristide embraced that plan, which would have allowed him to remain in power, but opposition leaders insisted he must go, bringing talks to a standstill.

The French proposal calls for establishing a politically neutral government of national unity, as in the Caricom plan, but also requires the election of a new president by summer. It foresees sending in human rights observers, relief aid and a United Nations representative.

It states, in roundabout language that French officials said should nevertheless leave no confusion, that Mr. Aristide must step aside. Mr. Aristide, who was ousted by a military coup in his first term and reinstated when the Clinton administration sent 21,000 American troops in 1994, has failed to compromise with his opponents and has ruled by decree since disputed elections in 2000.

According to Mr. de Villepin, President Aristide "bears heavy responsibility for the current situation."

"It is up to him to accept the consequences while respecting the rule of law," Mr. de Villepin said. "Everyone sees quite well that a new page must be opened in Haiti's history."

Administration officials said Wednesday, before the French proposal was made public, that they would continue to pursue a diplomatic solution, and would not support sending police officers or troops into a hostile environment.

"First things first," President Bush told reporters at the White House. He said the first step "is to work on a political solution."

John D. Negroponte, the American ambassador to the United Nations, expressed continuing support for the Caricom plan, which is also backed by the Organization of American States. Despite a flat rejection of that plan by the opposition leaders, the administration continued to press them to accept it.

"We continue to feel that support for the Caricom and the O.A.S. efforts to bring a peaceful political solution to the crisis in Haiti is — remains, in our opinion — the best way forward," Mr. Negroponte said. "We're disappointed that the opposition has rejected this plan, and we have not abandoned our hope that the parties can be persuaded to see the wisdom and the benefit of accepting such a plan."

Lawmakers warned the administration this week of the risks of more violence in Port-au-Prince. Nineteen members of the Congressional Black Caucus met briefly on Wednesday with the president, and with Secretary Powell and Condoleezza Rice, the national security adviser.

"The U.S. should play a major role in stopping the killing in Haiti," said one of the participants, Representative Kendrick B. Meek, whose South Florida district includes many Haitian-Americans. "We must not allow the thugs to storm the capital city."

Robert A. Pastor, a professor of international relations at American University, warned of the risks if Port-au-Prince were allowed to fall into the hands of armed gangs.

Unless the United States and other nations act "very quickly with military force" to halt the rebels, Dr. Pastor said, "they face a much harder decision: Who do you deal with then?" A display of force "could avoid the worst possible outcome: a civil war, and leadership emerging from a gang of drug-dealing thugs."