On Tuesday, Mrs. Clinton plans to attend a meeting in Honduras of the Organization of American States. Members of the group want to make an even clearer break with the past by moving to readmit Cuba, which the organization expelled in 1962, citing its alliance with the Communist bloc. Mrs. Clinton has fended off calls for Cuba to be offered membership until Havana moves to accept the group’s democratic principles. On Sunday, she reiterated that the United States would oppose the efforts of several Latin American countries to immediately reinstate Cuba.“We believe that membership in the O.A.S. comes with responsibility, and that we must all hold each other accountable,” she said. Cuba, for its part, has said it has no interest in returning to an organization that the official newspaper Granma referred to recently as “that decrepit old house of Washington.”