By CHRISTOPHER MARQUIS
 
WASHINGTON, Feb. 24 — Leaders of the Haitian opposition rejected an American-drafted proposal for a power-sharing arrangement with President Jean-Bertrand Aristide on Tuesday, increasing pressure on the Bush administration to send security forces to stabilize the country.

"There will be no more delays; our answer remains the same," Maurice Lafortune, head of the Haitian Chamber of Commerce, told The Associated Press. "Aristide must resign."

The action surprised Bush administration officials, who had drafted the power-sharing plan and seemed confident of their ability to deliver opposition support. But they secured the agreement only of President Aristide, whom they have accused of antidemocratic behavior.

The decision came despite lengthy debates and frequent phone calls from American officials, capped by an appeal — and a 24-hour extension — from Secretary of State Colin L. Powell, via conference call. The plan would have established a neutral government acceptable to all sides but would have left Mr. Aristide in office until his term ends in 2006.

Administration officials received the news shortly before a 5 p.m. deadline on Tuesday. They said they were determined to let diplomacy run its course and played down the possibility of sending in a multinational force. Canada and France have offered to send police officers to Haiti, but only in the context of a political settlement.

"People are still banking on not having to do that," one administration official said. "There are a bunch of other options out there." But he did not elaborate.

Canada's foreign minister, Bill Graham, said that the opposition were drafting a statement to send overnight to Mr. Powell, Reuters reported.

The State Department's point man for Haiti, Roger F. Noriega, faced sharp questioning in a closed session on Capitol Hill on Tuesday, as several senators accused the Bush administration of dithering in the face of a growing crisis, Congressional officials said.

"I think the U.S. hands-off policy is abdicating its responsibility," said Senator Bill Nelson, a Florida Democrat, after the session. "We're dealing with lives, here and now."

He and Bob Graham, Florida's other Democratic senator, have warned administration officials repeatedly of the potential for an exodus of Haitians to their shores.

Senator Mike DeWine, an Ohio Republican who has visited Haiti more than a dozen times in recent years, expressed disappointment at the opposition's rejection and said the United States should prepare to use force.

"If the situation continues to deteriorate, there's really no choice but to put together a military force to go into Haiti to stabilize the situation," Mr. DeWine said. "We have 20,000 U.S. citizens living in Haiti. You have the potential for a blood bath."

Administration officials were in contact on Tuesday with diplomats from France and Canada, officials said. Dominique de Villepin, the French foreign minister, has asked the European Union to approve funds for a peacekeeping force for Haiti, diplomats said, and France has invited representatives of Mr. Aristide and the opposition to come to Paris for talks.

Richard A. Boucher, the spokesman for the State Department, countered criticism that the administration had acted too casually on Haiti by saying the United States had been "at the forefront" of diplomacy.

"The point is to try to separate the politics from the violence and to try to move the political part of this forward in a way that we think can meet the needs both of the government and the opposition forces to have a meaningful role in government," he said.

But with the antigovernment uprising entering its third week and rebels setting their sights on the capital, Port-au-Prince, lawmakers warned that fighting could intensify.

Representative Kendrick B. Meek, a Florida Democrat, said the United States should intervene immediately. "The Bush administration has made it clear that it will wait until a number of Haitians are face down in the streets, and in the waters around Haiti, before they will act," he said.

Senator Christopher J. Dodd, a Connecticut Democrat with long experience in the region, said a force of even 1,000 would be be enough to help restore order. "It is too late for diplomacy alone to turn the tide there," he said.

Mr. Graham said the administration had done very little to ward off a possible flood of refugees. Thousands of Haitians took to the sea, often in flimsy boats, bound for Florida during the years of military rule after Mr. Aristide's ouster in 1991.

"From what I can tell, there is no Plan B," Mr. Graham said in remarks on the Senate floor on Tuesday. "There has been little or no contact between federal agencies and state and local authorities — our first responders — to prepare for the potential influx of refugees."

Mr. Graham noted that the Pentagon was "understandably hesitant" to send Haitian refugees to its naval base at Guantánamo Bay, Cuba; that is where nearly 600 suspected terrorists are being held.

"If we wait for a political settlement, we will be tolerating more scores of people being killed and more deaths due to the meager food supply and lack of adequate health services," he said. "If we continue to wait for a political solution, the country will be controlled by armed gangs, drug dealers and thugs."

Human Rights Watch urged the international community to send a peacekeeping force to Haiti to avert violent retaliation against supporters of President Aristide in the capital. "Given the horrendous human rights records of some of the leaders of the armed rebellion, we are extremely concerned," said Joanne Mariner, deputy director of the group's Americas Division.

The United Nations World Food Program, which lost a warehouse of food to looters in Cap Haitien on Sunday, warned that food shortages were inevitable if the situation continued to deteriorate. The program now supplies 373,000 Haitians.