By Andrew Cawthorne
                  Reuters
 

                  HAVANA, April 28—Cuban President Fidel Castro has rebuffed an
                  appeal for political reform and the release of political prisoners made by
                  Canadian Prime Minister Jean Chretien during a groundbreaking two-day
                  visit here.

                  After seeing Chretien off at the airport today, Castro declared: "We are
                  not going to change; we are going to continue defending our cause and our
                  socialism." The Cuban leader made it clear he would not bend to pressure
                  either from declared foes, such as the United States, or would-be friends,
                  such as Canada.

                  Cuba's Communist revolution "is the biggest change there's been in history,
                  and we're not going to renounce that," Castro said when asked about
                  Chretien's pleas. Chretien had appealed in particular for the release from
                  prison of four leading political dissidents, but Castro gave no indication he
                  would comply.

                  "We have not made any type of commitment in relation to that," Castro
                  said. He added pointedly that Cuba is not the only nation with prisoners
                  charged with crimes against the state, declaring that there are "hundreds" of
                  such inmates in Europe.

                  Chretien arrived in Cuba Sunday on a mission that was meant to stress
                  both Ottawa's independence from the U.S. policy of seeking to isolate
                  Castro's Communist government and its belief that "constructive
                  engagement" with Havana could bring political change here.

                  On the plane back to Ottawa, reporters asked Chretien repeatedly if he
                  thought his mission had failed because it produced few concrete results. "I
                  take one step at a time," Chretien said, adding that it is possible the two
                  leaders might meet again in Geneva next month when both attend an
                  international event.

                  He said also that it is likely he will brief President Clinton in Britain next
                  month during the annual summit of the Group of Seven industrial
                  democracies. No other member of the group -- which consists of the
                  United States, Germany, Japan, Britain, France, Italy and Canada -- has
                  sent a government leader to Cuba.