TORONTO -- His constituents flock to Cuba by the thousands for sun-drenched vacations, but Canada's prime minister will feel a different kind of heat when he goes there next week.

From Washington -- and from human-rights groups and opposition politicians at home -- Jean Chretien is under intense pressure to prove that meeting Fidel Castro can produce meaningful advances in human rights.

His aides are trying to play down the prospects for any major breakthroughs during the Sunday-through-Tuesday visit, but that hasn't quieted the skeptics.

``We'd like to see the prime minister use his influence to improve human rights in Cuba,'' said Preston Manning, leader of the right-wing Reform Party. ``We want to see him talking about that with Castro on television, not in some back room.''

The national chapter of Amnesty International, editorial writers in left-leaning and right-leaning newspapers, and Quebec separatist leaders all have urged Chretien to take a tough line on human rights during his visit.

For nearly four decades, Canada's tolerant policy toward Cuba has been one of the few steady sources of friction with the United States.

The Clinton administration has expressed muted disapproval of Chretien's trip, acknowledging that he has a right to go, but expressing doubt that he will prod genuine reforms.

Among U.S. conservatives, the reaction has been harsher. Marc Thiessen, a spokesman for Sen. Jesse Helms, R-N.C., called the trip ``a waste of time, nothing more than a 30-hour photo op.'' He urged Chretien to meet with dissidents and former political prisoners.

Helms is co-sponsor of the 1996 Helms-Burton law, which seeks to discourage foreign investment in Cuba by punishing companies using property expropriated from Americans after the 1959 revolution.

As one of Cuba's largest trading partners, Canada is a prime target of Helms-Burton. Toronto-based Sherritt International is one of a handful of companies worldwide to incur the penalty of having its executives barred from the United States.

Overall, Helms-Burton had failed to dent Canada's interest in Cuba. Two-way trade has more than doubled during the past four years, and Canadian tourists have increased from 142,000 to 169,000 a year since 1995.

``Isolation leads nowhere,'' Chretien told Parliament this week. ``But if we are engaging them, discussing with them, offering help . . . the people of Cuba and the president of Cuba will certainly be happy to have a dialogue.''

Archibald Ritter, a Canadian economist who has taught market economics in Havana, predicted Chretien would try to talk tough to Castro, but not in front of the cameras.

``I think Chretien will be forthright and frank -- he won't beat around the bush,'' Ritter said. ``But he'll probably do that behind closed doors.''

Almost certainly, Chretien won't emulate the last Canadian prime minister to visit Cuba. In 1976, on a visit that outraged many Americans, a shirt-sleeved Pierre Trudeau shouted during an outdoor rally, ``Viva Cuba, Viva Fidel Castro.''

This time, the Canadian foray fits Cuba's gradual emergence from isolation. Pope John Paul II's recent visit helped persuade Chretien to go, and many Latin American leaders at the recent Summit of the Americas in Chile spoke favorably of reintegrating Cuba into hemispheric activities.

In Havana, Chretien's trip has been welcomed as a blow against U.S. policy.

``It shows that we are not isolated, not even from close allies of the United States like Canada,'' said Deborah Ojeda, the Canadian desk officer at the Cuban Foreign Ministry.

Canada's foreign minister, Lloyd Axworthy, last year joined Castro in signing an outline for Canada to help Cuba improve human rights.

``We're not looking for breakthroughs, we're looking for progress,'' Axworthy said this week. ``And I think we have had progress.''