TORONTO -- Warming up for bigger battles ahead, the scrappy Canadian Auto Workers union leader Bob White has taken his 4,000 members at a Boeing Co. plant here out on strike to teach the U.S. aircraft company a lesson or two about the relative power of unions in Canada compared to their American counterparts.

In their first negotiations since Boeing bought the money-losing de Havilland Aircraft Co. from the Canadian government last year, White has taken personal offense at the hard-nosed take-it-or-leave-it Boeing demand for concessions by the union. He has accused Boeing of "trying to impose a U.S. system of labor negotiation that is totally foreign to this country."

Flashing a broad boyish grin, White said in an interview, "We're saying very clearly to Boeing, 'Don't try that here, my friends.' "

The deceptively slight and low-key White, 52, is regarded by managers who have dealt with him as a formidable adversary.

As the head of the 150,000-member Canadian Auto Workers union, he is the best-known labor leader in Canada, a country where militant unions are not only still potent forces at the work place but also are gaining in influence in the currently volatile national political arena.

The big test for White began last week when he started simultaneous negotiations with the Big Three auto manufacturers, the first since he pulled the Canadian affiliate out of the United Auto Workers union after bitter, protracted divorce proceedings.

The split, formalized last year, arose during a General Motors negotiation in 1984 when Canadian workers rejected job security and profit-sharing elements of GM's settlement with U.S. auto workers, preferring a more traditional combination of guaranteed wage increases and cost-of-living allowances.

Last week, after opening contract talks with General Motors Corp. negotiators, he said, "This is not a test for the CAW but it is a test for GM. If our priorities and direction are different from the industry in the U.S., will GM be able to make that separation?" He said the Canadian union's demands include pension improvements, raises in base wage rates and better income protection for laid-off workers.

During the fateful round of bargaining with GM three years ago, White allowed a documentary film crew inside the negotiations, and the program, titled "Final Offer," was aired a year later at prime time across the country on the Canadian Broadcasting Corp. network.

In the unusual look at the inner workings of collective bargaining, the tensest battles were not between White and GM negotiators, with whom his relations were comparatively amicable, but with UAW chieftain Owen Bieber. White laughs mischievously now when recalling Bieber's reaction upon learning what the film crew was doing. "Owen went absolutely bananas at me because he said it was a breach of faith and this was an internal thing in the union and I had no right to expose it."

White's recent public blasts at Boeing, where union members have been on strike since June 23, did not go unnoticed by the auto companies. A few days after his remarks, Ford Motor Co. of Canada President Kenneth W. Harrigan, carefully choosing his remarks about the upcoming auto negotiations, said in a speech, "It is our belief that we should be talking with the Canadian Auto Workers, and not at them, and we both have a lot to talk about."

Last week, Rick Curd, GM's chief negotiator, stressed that he is willing to "negotiate a Canadian agreement in a Canadian context."

White's heady self-confidence and his pointed appeals to a bruised Canadian sense of national pride have made him something of a folk hero in a country where U.S. influences are pervasive. Even business people who strongly oppose his demands and his left-leaning political views fawn over him when he speaks at civic clubs, although lately some people, including a few fellow unionists, are beginning to question whether he is more than a bit ruthless, out to build a mighty empire by raiding other unions.

He currently is the target of lawsuits and an effort to have his union ousted from the umbrella Canadian Labor Congress as a result of the decision in March by the 23,000-member Newfoundland-based fishermen's union to sever its affiliation with the U.S. United Food and Commercial Workers International in order to join the Canadian Auto Workers.

As the mildly socialist New Democratic Party, of which he is a vice president, has surged from its traditional third-place ranking in national public opinion polls to take the lead in recent months, many observers also wonder about his political ambitions.

"At this point in my life, I don't see myself going into politics," he said in the interview. "I have used the glib remark that I'd love to be prime minister but I can't stand the apprenticeship program ... . I don't know quite frankly what I'm going to do."

One thing he is attempting to do is to build a political organization in the auto plants and he is urging his shop stewards to speak out and get involved in political issues. He argues that strong political leverage is essential to safeguard Canadian industrial jobs in a period of contracting labor forces and strong competition from abroad.

White is one of the principal opponents to Prime Minister Brian Mulroney's initiative for a free trade deal with the United States. He said he is strongly concerned about possible changes in the 1965 Canada-U.S. auto pact, which removed tariffs on motor vehicles and parts and contains safeguards requiring manufacturers to maintain levels of production in Canada related to the value of their sales here.

"It is perfectly clear that free markets have, and will continue to, fail," he said in a speech. "Social-political sovereignty demands a measure of economic sovereignty. And that's what the free trade debate is fundamentally about. What kind of Canada do we want? Do we accept what exists in the U.S. as the upper limit on what we can build and achieve? Or do we have the confidence and vision to build a different, more progressive society on this side of the North American continent?"

If White is sharply critical of what he describes as the "Rambo, survival-of-the-fittest" philosophy of the Reagan era, he is just as biting about U.S. union leadership for agreeing to wage rollbacks and other concessions.

"I was arguing that, of course, workers want to save their jobs but the leadership of the labor movement should be telling them that giving up these wages doesn't naturally mean you're going to save your job," he recalled. "One of my statements was workers don't need a union to walk them backwards; they can do that on their own."

White acknowledged that the more liberal Canadian political climate and the absence of any large nonunionized region like the U.S. South relieves him of some of the pressures his U.S. colleagues face. Over the past decade, as U.S. unions have steadily lost share of the labor force, Canadian unions have penetrated more deeply. By 1985, about 40 percent of nonagricultural workers in Canada belonged to unions, compared with only about 18 percent of their U.S. counterparts.

White -- who still speaks with the lilt of his native Northern Ireland, from which he emigrated with his parents when he was 13 -- dismisses the suggestions of business people and commentators that he has imported to Canada British-style unionism. His hero in the labor movement was Walter Reuther, the only labor leader whose photograph graces the wall of his office in suburban Toronto.

The only point at which his voice waxed emotionally during the interviews was when he remembered the first time he attended a UAW convention in the mid-1950s, when Reuther was president. "I was spellbound and I got to meet him and watch him and he's the person who really instilled in me a lot of what the UAW was about -- about not just collective bargaining but a social union involved in civil rights and international affairs and political issues."

But whether he can continue to adhere to a 1950s brand of U.S. unionism, even in Canada, is open to question. The auto industry is booming in Canada now because of the cheaper Canadian dollar, which lowers labor and operating costs. But the auto manufacturers have already signaled that they, like Boeing, want more flexibility in the work place, progress on bringing down an absenteeism rate that is nearly double that of the United States, and some relaxation of the rigidity of the union force here where one- or two-hour wildcat strikes are frequent.

White has kept his cards close to his chest, keeping the auto makers guessing about whether he will deliberately target one of them.

In the interview, he said he believed that in coming years there will be a contraction in his union. His efforts to expand by organizing workers at a Michelin Tires Ltd. plant in Nova Scotia earlier this year failed. Japanese and Korean auto companies establishing plants in Canada have cleverly located them on the countryside, away from the union hotbeds, and they will likely be difficult to organize.

Magna International, one of the major Canadian auto parts manufacturers, has successfully staved off unions by giving generous benefits and incentives and distributing 10 percent of the company's pretax profits to the firm's 9,000 employes.

Meanwhile, White must face the music at a Canadian Labor Congress meeting next week to consider the raiding charges against him. He appeared undaunted by the prospect.

"I think we're still going to be in the House of Labor," he said, smiling confidently. "I think there will be some people who will want us to be publicly whipped in front of Toronto City Hall for all of this."

Washington Post researcher Nancy Kroeker contributed to this report.