MIAMI — America has a message for the millions of Haitians left homeless and destitute by last week’s earthquake: Do not try to come to the United States.

Every day, a United States Air Force cargo plane specially equipped with radio transmitters flies for five hours over the devastated country, broadcasting news and a recorded message from Raymond Joseph, Haiti’s ambassador in Washington.

“Listen, don’t rush on boats to leave the country,” Mr. Joseph says in Creole, according to a transcript released by the Pentagon. “If you do that, we’ll all have even worse problems. Because, I’ll be honest with you: If you think you will reach the U.S. and all the doors will be wide open to you, that’s not at all the case. And they will intercept you right on the water and send you back home where you came from.”

Homeland Security and Defense Department officials say they are taking a hard line to avert a mass exodus from the island that could lead to deaths at sea or a refugee crisis in South Florida. Haiti’s capital, Port-au-Prince, is about 700 miles from Miami.

So far, there has been no sign of Haitians trying to flee the island by boat, United States officials say. Nor has there been a mass exodus of Haitians into the neighboring Dominican Republic, except for about 3,000 injured people who are being treated at hospitals just over the Dominican border, officials there say.

But United States officials say they worry that in the coming weeks, worsening conditions in Haiti could spur an exodus. They have not only started a campaign to persuade Haitians to stay put, but they are also laying plans to scoop up any boats carrying illegal immigrants and send them to Guantánamo Bay, Cuba.

Department of Homeland Security officials have also transferred 200 illegal immigrants from the Krome Service Processing Center here — a federal jail for people awaiting deportation — to make room for a possible influx of Haitian migrants.

The State Department has also been denying many seriously injured people in Port-au-Prince visas to be transferred to Miami for surgery and treatment, said Dr. William O’Neill, the dean of the Miller School of Medicine at the University of Miami, which has erected a field hospital near the airport there.

“It’s beyond insane,” Dr. O’Neill said Saturday, having just returned to Miami from Haiti. “It’s bureaucracy at its worse.”

Customs officials have allowed a total of 23 Haitians into the United States on humanitarian grounds for medical treatment, said a spokesman for the Department of Homeland Security.

And late Monday, Homeland Security Secretary Janet Napolitano said the United States would allow some orphaned children to enter the country temporarily on an individual basis.

A State Department spokesman, Noel Clay, said the United States had not suspended its visa requirements for Haitians trying to flee the disaster, even though the Department of Homeland Security has halted the deportations of Haitians already in the United States illegally.

“We urge Haitians in Haiti not to put their lives at additional risk by embarking on a dangerous sea voyage,” Mr. Clay said.

In the Dominican Republic, officials have adopted a similar stance. The secretary of foreign relations has ordered only Haitians with medical emergencies allowed into the country, and the Army has established checkpoints on roads leading from the border.

Sandra Severino, a spokeswoman for President Leonel Fernández, said there had not been a huge spike in illegal immigration on the border, and indeed many Haitians already in the Dominican Republic are returning to help their families.

Officials in the Bahamas, which has a large Haitian population, are also keeping a close watch on the seas, but have not noticed a surge in boats carrying refugees, said the deputy prime minister for foreign affairs, T. Brent Symonette. He added that the Bahamas would not repatriate immigrants arriving from Haiti immediately, given the severity of the humanitarian crisis.

Few experts on immigration expect droves of Haitians to take to the seas in flimsy boats right away, though they add that it is hard to predict what will happen in the coming weeks. Most earthquake victims are still struggling to find food and water; they are in no condition to plan and provision a sea voyage. In addition, the Coast Guard currently has five cutters patrolling Haitian waters.

Lt. Commander Chris O’Neil said the Coast Guard had not spotted any boats leaving Haiti with refugees on Monday. “None, zero,” he said, “and no indication of anyone making preparations to do so.” He said anyone caught leaving the island and heading toward Florida would be returned to Haiti.

www.nytimes.com/2010/01/19/us/19refugee.html