The diplomatic initiative is the highest-profile effort by the Bush administration to resolve the growing crisis in Haiti.

"The bottom line is, we have to see the formation of a new government that will perform fully its constitutional role," a State Department official said. He added that the government must "be able to inspire confidence by virtue of its composition and independence."

Assistant Secretary of State Roger Noriega will be the U.S. representative in the mission. With security conditions rapidly deteriorating, the State Department also urged U.S. citizens to leave Haiti, and the Pentagon announced it is sending a four-man military team to assess security at the U.S. Embassy there and prepare for a possible emergency evacuation.

Defense officials said the dispatch of the team should not be viewed as an initial step toward U.S. military intervention. Since the outbreak of violence last month, the Bush administration has rejected the idea of sending U.S. troops or police to Haiti, saying it prefers to help broker a political solution.

Still, the Pentagon move, which officials said came at the request of the U.S. ambassador to Haiti, James B. Foley, underscored administration concerns about security in the country, with opposition groups in control of a number of towns and dozens of people dead.

A State Department statement said Peace Corps personnel were being withdrawn and authorization has been given for the family members of U.S. Embassy personnel and some embassy employees to leave voluntarily.

A nighttime curfew has been imposed on the embassy's remaining staff and their relatives, the statement said, and travel by the staff outside of Port-au-Prince, the capital, has been prohibited.

The statement also warned that the embassy's ability to provide emergency services to U.S. citizens outside the capital is limited and has "drastically decreased in recent days due to numerous random roadblocks set up by armed groups." It urged U.S. citizens to leave while commercial airliners "are still operating on an uninterrupted schedule."

While citing attacks on government facilities by opposition groups, the statement also blamed the violence on pro-government groups and on Aristide himself. "Haiti's security environment has been deteriorating as President Aristide has continued to politicize the Haitian National Police and used government resources to pay for violent gangs to attack opposition demonstrators," the statement said. "The government of Haiti has failed to maintain order in Port-au-Prince or in other cities and in some instances has assisted in violently repressing the demonstrations."

Canadian Foreign Minister Bill Graham told reporters in Ottawa "there are concerns" that Aristide is not living up to his promises to release certain political prisoners, appoint a prime minister who would be independent of the presidency and reform the police.

"There is a time limit" for Aristide to comply, Graham said. Without specifying how long Aristide might have to implement the reforms, Graham said, "It cannot go on forever."

But Secretary of State Colin L. Powell, in an ABC Radio interview yesterday, said Aristide's early departure, which some opposition leaders have demanded, is "not an element" of the international diplomatic initiative being undertaken "because under the constitution he is the president for some time to come yet."

Powell held out the possibility that as part of negotiations with opposition leaders, Aristide might agree to leave ahead of the scheduled end of his term in February 2006. "But right now he has no intention to step down," Powell added. "And since he is the elected leader of Haiti, we should not be putting forward a plan that would require him to step down."