WASHINGTON (CNN) -- The U.S. Immigration and Naturalization Service
                  is threatening to revoke Elian Gonzalez's parole status by Thursday, if the
                  6-year-old immigrant's Miami relatives don't give their written promise to
                  relinquish custody of him if they lose their court battle for custody.

                  The message came Monday night in a letter from INS Executive Associate
                  Commissioner for Field Operations Michael Pearson to Spencer Eig, lead
                  attorney for Elian's great-uncle Lazaro Gonzalez, who has been fighting to
                  keep Elian from being returned to his father in Cuba.

                  The letter says it "remains necessary" for Eig to appear at the INS district
                  office in Miami at 9 a.m. Tuesday for a face-to-face meeting with INS
                  District Director Bob Wallis.

                  The letter says it is "advisable" for Lazaro Gonzalez to attend the meeting.
                  Pearson says, however, if Lazaro is not there Tuesday, he should appear at a
                  follow-up meeting Wednesday. "It will not be necessary to bring Elian to the
                  meeting," Pearson said.

                  Letter follows appeal announcement

                  The letter came on the same day the 11th U.S. Circuit Court of Appeals agreed
                  to hear an appeal by the Miami relatives to reverse a lower court decision that
                  allowed the Justice Department, which oversees the INS, to force the boy's return
                  to Cuba.

                  The court gave attorneys for the relatives until April 10 to file their appeal, and
                  arguments in the case have been scheduled for the week of May 8 in Atlanta.

                  Earlier Monday, the INS told an attorney for Lazaro Gonzalez that because he
                  has refused to promise to give up custody of Elian if that appeal fails, the federal
                  government will revoke the boy's parole status which has allowed the great-uncle
                  to maintain temporary custody of the boy.

                 An 'excuse to arrest Elian'

                  Eig said the Miami relatives were not in violation of the government's ultimatum
                  and said the Justice Department is looking for an "excuse to arrest Elian."

                  "INS has asked Lazaro Gonzalez to sign a piece of paper guaranteeing that
                  he'll do anything they tell him to do," Eig said. "No Attorney would ever
                  advise a client to sign such an open-ended guarantee."

                  The letter echoed that warning. "You have never provided us with a simple,
                  clear statement that your client is willing to produce the child when requested
                  to do so by the INS," the letter said.

                  "Without a specific written commitment ... we have no choice but to move
                  forward with the termination of Elian's parole as of Thursday, March 30, 2000
                  at 9:00 a.m.," the letter said.

                  If Lazaro Gonzalez decides to sign an agreement recognizing the authority of
                  the INS, and promises to relinquish Elian if the appeal fails, the parole status
                  will not be revoked the letter said.

                   The government letter does not indicate when or how federal authorities will
                   arrange for the transfer of Elian's custody if it gets to that point.

                   Elian was found clinging to an inner tube off the Florida coast last November
                   25. He was one of three survivors of a shipwrecked immigration mission from
                   Cuba, that left his mother, step-father and nine others dead.

                  Since the start of the case, the Miami relatives and their supporters among the
                  Cuban exiles community have contended that the boy would face a miserable
                  future if he was returned to Cuba.

                  But Castro, saying the boy has been "kidnapped" by his great- uncle Lazaro
                  Gonzalez and what he terms the Miami "mafia," has mobilized huge protests in
                  Cuba to call for his return.

                 Havana calls for 'drastic action'

                  In a speech on Sunday, Castro said some Cubans were now calling for drastic
                  action to obtain Elian's return, up to and including an armed rescue mission.

                  Other views cited by Castro as "spontaneous opinions from the people" called
                  for a blockade of the U.S. diplomatic mission in Havana and an opening of
                  Cuba's frontiers to unleash a flood of migrants toward the United States.

                  Castro said subjecting Elian to the television interview was "monstrous and
                  sickening."

                  "You cannot do this without the authorization of the father," said Castro. "I
                  sincerely think that this boy is at risk in the hands of desperate people and the
                  government of the United States should not be running this risk."

                  Producer Terry Frieden, Correspondent Susan Candiotti, The Associated Press and Reuters contributed to this
                                             report.