BY ALFONSO CHARDY

  Coast Guard cutters operating off South Florida's shores have picked up fewer Cuban migrants in the first three months of the year than Haitians and Dominicans
  combined. But the absence of large numbers of Cuban migrants headed for South Florida may be the calm before the storm.

  A wave of repression in Cuba in recent weeks has been so alarming that U.S. officials have begun to wonder whether Cuba may unleash a new Mariel-style exodus -- a typical Cuban response in times of crisis. American officials are so worried that they have already quietly advised Cuba not to attempt any such action.

  But if a new exodus occurs, officials say they will activate a classified federal contingency plan designed to deal with migrant surges. Operation Distant Shore would trigger a dramatic escalation in the number of Coast Guard and other military vessels patrolling the Florida Straits -- a veritable floating wall designed to interdict as many migrants as possible at sea.

  Talk of the plan is all the more relevant in the wake of reports last week that President Bush was preparing punitive steps against Cuba along with a possible public
  warning to Fidel Castro not to resort to a new exodus. No one will say when Bush would deliver the warning, but officials at the White House's National Security Council and the State Department have left no doubt that Washington is concerned.

  ''The United States remains committed to safe, legal and orderly migration from Cuba to the United States,'' National Security Council spokesman Sean McCormack said.

  ''We make clear to Cuba that the United States expects it to live up to its commitments under the migration accords,'' a State Department official said.

  ANONYMOUS REPORTS

  While neither official would say what the administration is planning in response to a recent crackdown against Cuban dissidents, administration sources have floated
  anonymous reports that among the more drastic measures are a possible halt to cash remittances to exiles' relatives in Cuba or an end to direct flights to the island.

  Responding to U.S. threats, the Cuban government published a statement Friday saying that U.S. sanctions would not bother Cuba but might encourage illegal migration.

  ''The presumed measures that are being announced of prohibiting flights and remittances would stimulate illegal immigration,'' the Cuban statement said.

  Later Friday, Cuban Foreign Minister Felipe Pérez Roque told a news conference that three imprisoned hijackers were executed last week to prevent a ''migration crisis'' that could spark war between the United States and Cuba.

  ''It was an exceptional step, a painful measure, taken as a last resort and founded on the hope of avoiding greater loss of life and costs for both countries, [including] the unleashing of a new migration crisis that would end with a war between the two countries,'' Pérez Roque said.

  NO IDLE FEAR

  Some American officials fear that if the United States enacts new steps to inflict punishment on Cuba, then Havana might retaliate by unleashing a new migrant exodus to punish the United States. It's not an idle fear.

  Three times since Castro seized power in 1959, Havana has deliberately encouraged thousands to reach South Florida on boats or rafts. After Mariel, in 1980, officials on this side of the straits came up with a plan, which has been periodically updated. The exact plan remains secret, but a few details are known:

  •  The first step would be to determine whether an exodus is under way.

  Luis Díaz, a Coast Guard spokesman in Miami, said it would require the spotting of hundreds of migrants headed to South Florida in one day to trigger a decision on
  whether to activate the plan.

  •  Once the plan is operational, Díaz said, the Coast Guard would pull reinforcements in from other districts, adding extra cutters to patrol off South Florida shores.

  •  If senior federal officials agree, military vessels would rush to assist the Coast Guard in picking up migrants.

  •  Once military personnel are involved, command for military activity would switch to the U.S. Southern Command in Miami-Dade County.

  ''If there was a mass migration, we would be the unified command,'' said Lt. Cmdr. Chris Loundermon, a Southern Command spokesman.

  •  If Cuba does not take back interdicted migrants, some might be brought to the U.S. Naval Base at Guantánamo Bay, Cuba, and others to other countries in the region.

  •  Finally, while the plan is designed to prevent the bulk of exodus migrants from reaching U.S. shores, components of the plan assume that some may get through. If that happens, federal, state and local authorities would collaborate under the emergency plan to house and process exodus migrants who reach shore.

  A senior federal official who has seen copies of the plan said that while the migrants would be received in South Florida, they would likely be taken eventually to military installations around the country for processing.

  Some Cuba analysts in the United States believe that the Camarioca departures in 1965, the Mariel boatlift in 1980 and the rafter exodus in 1994 were ''engineered
  migrations'' -- political weapons designed to punish the United States for real or imagined actions and coerce it into softening policies toward Cuba.

  Cuba expert Kelly M. Greenhill argued in a landmark study last year of Cuban mass migrations that Castro launched the rafter exodus to ''manipulate'' fears in the United States of another Mariel to compel a shift in U.S. policy toward Cuba.

  The exodus ended when the United States and Cuba began to negotiate new migration accords under which Washington eventually agreed to return migrants stopped at sea to Cuba. Until then, Cuban migrants rescued at sea were brought to the United States and allowed to stay.

  While Cuba welcomed the change in migrant policy, it was not totally satisfied, since Cuban migrants who manage to reach shore still get to stay.

  Greenhill, a research fellow at the Olin Institute for Strategic Studies at Harvard University, said the circumstances of the current Cuban crisis should be monitored closely for signs of a possible new exodus. ''I would say that the situation bears close watching,'' he said. But he added that Castro might think twice before sanctioning a new exodus.

  ''I don't think it's impossible we could see another outflow,'' Greenhill said, ``but if I were Castro, I'd think long and hard about launching an engineered migration this time around, given the prevailing environment in the aftermath of Sept. 11 and Iraq. The world looks different today than it did in 1965, 1980 and 1994.''

  MOTIVE UNCLEAR

  Precisely what would prompt Cuba to unleash another exodus is not known. Better known is what initial steps the United States would take if another exodus begins.

  The new Department of Homeland Security has in place an agreement with Florida state officials, signed in 1998, that would enable state law enforcement officers to assist federal immigration officials in processing large numbers of refugees.

  Zachary Mann, a spokesman for immigration and customs enforcement and customs and border protection in Miami, said the emergency plan was reviewed and
  reevaluated last year.

  ''We came up with new strategies and options to deal with mass migration,'' he said, without giving details. ``It's something we constantly try to be ready for.''

  More than 40 federal, state and local agencies are believed to be part of the plan, including South Florida police departments.