BY NANCY SAN MARTIN

  The threat by Cuban President Fidel Castro to possibly close the U.S. diplomatic mission in Havana and dissolve bilateral migration accords sets the stage
  for a potential crisis and should be taken seriously, according to a wide range of experts.

  Castro issued the warning earlier this week during a speech delivered at the National Assembly hours before lawmakers unanimously approved an
  amendment to make the socialist-framed constitution ``irrevocable.''

  ''It's really quite a startling speech,'' said Georgetown University Adjunct Professor Brian Latell, a retired Central Intelligence Agency analyst and an
  expert on Cuba and Castro.

  ''This is Castro at his paranoid worst,'' he said. ``I think it's very threatening.''

  The warnings have raised concern that Castro is prepared to unleash another massive exodus of migrants to get rid of alleged malcontents, a tactic he
  has used three other times during his 43 years in power -- in 1965, 1980 and 1994.

  ''It's always a viable threat and it's always something [Castro] uses to loom over the United States,'' said Eugene Pons of the University of Miami's
  Institute for Cuba and Cuban American Studies. ``You really can't predict anything with Castro. From a U.S. perspective, they should be extremely
  vigilant.''

  SEVERAL FACTORS

  Castro's outburst, analysts said, is driven by a number of factors, including a worsening economy, no immediate easing of the economic embargo and
  more visible activity among the political opposition.

  Washington officials have said that breaking off the migration accords would be a mistake and defended the work of U.S. diplomats in Havana, which
  recently has included the distribution of short-wave radios so Cubans can tune in to the U.S.-funded Radio Martí.

  The Bush administration also has backed increased funding for organizations that help propel the dissident movement on the island.

  Florida Gov. Jeb Bush, during a visit to Miami this week, said that abandoning the migration accords would be considered an ''act of aggression,'' and that
  the United States would react strongly to a new exodus.

  DISTURBED BY WORDS

  Even supporters of improved relations between the United States and Cuba were disturbed by Castro's words.

  ''I was very disappointed because I have certainly been privy to private conversations with Castro in which he has expressed a desire to turn the page,''
  said Sally Grooms Cowal, president of the Cuba Policy Foundation, which advocates lifting the economic embargo against Cuba.

  ''I hope that this was just a hot June day and it will go away in July,'' she said. ``If not, you can forget about any legislative process on ending the
  embargo or anything else.''

  Castro has always used ''anti-imperialist'' rhetoric in remarks aimed at the United States. But unlike his frequently rambling addresses, this speech was
  methodical, rife with militant undertones directed at President Bush.

  ''Around the time when he assumed office, we wanted to avoid any rhetorical exchanges with the new president of the United States,'' Castro said.
  ``Even though we didn't have the slightest doubt about his Cuba policy, we didn't see the point in casting the first stone. We would be patient.''

  Among the things the Cuban government blames the Bush administration for is a citizens' initiative known as the Varela Project that seeks a referendum
  on changes to Cuba's social, economic and political structure. Castro has said the campaign is the work of the U.S. Interests Section, and the National
  Assembly's move to keep the socialist system intact is viewed as the government's response to the grass-roots effort.

  ''We are not the ones attacking, being hostile to or blockading the United States,'' Castro said. ``We are not demanding that its constitution and political
  and economic system be changed. We show the strictest respect for the rights of other countries. Our rights must also be respected.''

  SERIES OF EVENTS

  Among the incidents and activities Castro cited to justify his rhetoric:

  • The U.N. censure of Cuba for human rights violations.

  • Public accusations by U.S. officials that Cuba is involved in biological weapons research.

  • Speeches by President Bush in both Washington and Miami on May 20, vowing to maintain the trade embargo until democratic elections are held on the
  island.

  • The State Department's continued inclusion of Cuba as a state that sponsors terrorism.

  • A June 1 commencement address by Bush that centered around preemptive strikes as part of a new U.S. doctrine for the fight against terrorism.

  ''The responsibility will lie with the U.S. government if its repeated commission of such offenses leads to the cancellation of the migration agreement and
  even to the withdrawal of the U.S. Interests Section in Havana,'' Castro said.

  The speech ends with Castro directly telling President Bush that he is not afraid of the consequences.

  ``It is not my purpose to offend you personally, but I can tell you this because I have the modest possibility of meditating with objectivity and because,
  together with our valiant and heroic people, I lost long ago any notion of fear.''

  ''The Cuban government is weighing its words very, very carefully,'' Latell said. ``[Castro] is throwing down the gauntlet.''