TORONTO, JULY 27 -- The premiers of Canada's four western provinces agreed today to seek a unified stand in redefining the region's role in a looser Canadian confederation following the collapse last month of constitutional amendments that were intended, in part, to give more power to the provinces.

In a meeting that underscored the centrifugal forces of regionalism that have long beset Canada, and that have been exacerbated by the country's failure to ratify the constitutional amendments, the western provincial leaders agreed to seek a "blueprint for the new realities of the 1990s."

The premiers said they will explore the possibility of jointly collecting income taxes on a regional basis in order to remove what they said is a "federal bias" in the distribution of public money, and also will consider "disentanglement" from certain federal social programs.

"Our economic priorities might better be served if western Canada did it {collected taxes} instead of having it done federally," said Saskatchewan Premier Grant Devine. Currently, the central government collects income taxes in all provinces except Quebec and redistributes money to the provinces in federal transfer payments.

The stage for the western premiers' decentralizing moves was set June 23 when Manitoba and Newfoundland refused to join the country's eight other provinces in ratifying the Meech Lake accord. The accord, named for a Quebec resort where the agreement took shape, would have given predominantly French-speaking Quebec special status as a "distinct society," a concession aimed at getting Quebec to sign Canada's 1982 constitution.

While the speeches at today's meeting at Lloydminister, Saskatchewan, were largely rhetorical and produced few specific strategies, the western premiers put the central government in Ottawa on notice that western Canada intends to look out for its own interests as Quebec seeks a more autonomous political arrangement with English Canada.

While supporters of strong federalism accuse the western premiers of picking at the bones of a fragmenting confederacy for their own economic advantage, today's meeting appeared in part to be muscle-flexing for the benefit of rival political parties, including the burgeoning, three-year-old Reform Party.

The Reformers, a western-based populist group led by 47-year-old business consultant Preston Manning, have elected only one member to Parliament, but polls show that the party could sweep a provincial election in Alberta if one were held now. It also is gaining strength in British Columbia, according to surveys.

While not a separatist movement, the Reform Party focuses largely on the western provinces' sense of alienation from the rest of Canada and of underrepresentation in the nation's political institutions.

Another group that has sprung up in Alberta recently is the secessionist Western Independence Association, which envisions a new republic called Canada West and which has a constitution and a flag that replaces the maple leaf with a silhouette of the Rocky Mountains.

Although the association has yet to make any significant political impact, one of Canada's leading pollsters and analysts of western trends, Angus Reid, recently said in Toronto's Globe and Mail newspaper, "If we go through 10 years of constant focus on Quebec, that will make the west more vulnerable to the fringe groups."

There are other organized forces of regionalism at work in the Pacific Northwest, including some which straddle the U.S.-Canadian border. A new, Seattle-based policy group called the New Pacific is promoting a concept in which Washington state, Oregon and British Columbia would form an informal trading bloc.

The editor of the group's quarterly policy journal, Eileen V. Quigley, spoke of a cross-border region she calls "Cascadia," with an area of 529,000 square miles and a population of more than 10 million people. Such an arrangement would give British Columbia the economic independence it seeks, while at the same time making the U.S. Pacific Northwest a major regional power.

Citing the emergence of global markets, Quigley said the U.S. Pacific Northwest and British Columbia region "is well on the way to becoming an international bridge across which people, products and cultures will flow, connecting the Pacific Rim and even much of the Soviet Union with the United States."

Her view was echoed by Saskatchewan's Devine, who stressed the need for cross-border regionalism. "The {U.S.} western state governors feel much the same, he said. "We need to identify common strengths . . . and build on those so we can catch up with other regions and lead them."

Alberta and British Columbia already have begun negotiations for informal trading agreements with Alaska, Idaho, Montana, Oregon and Washington to lessen their dependence on central Canada.

What is uncertain is whether the western provinces can merge the interests of oil-rich Alberta and British Columbia, which has received a massive infusion of Hong Kong money, with the interests of poorer, rural provinces like Saskatchewan and Manitoba, which are mainly concerned with cutbacks in payments from the federal government to the provinces.