TORONTO, JUNE 10 -- A fragile agreement by federal and provincial leaders aimed at keeping Quebec in the Canadian confederation appeared to be unraveling tonight as Newfoundland's premier said he was put under "extreme pressure" to sign the accord Saturday night and will leave the decision either to his provincial legislature or to a referendum.

"I will not allow that kind of pressure tactic to deny the people of Newfoundland from having their say," said Premier Clyde Wells, hinting that he favors a provincial referendum on the constitutional amendments even if it cannot be held before the June 23 deadline.

Wells, who Saturday night said he had signed the constitutional changes because he put "Canada first and Newfoundland second," tonight said he would advise Newfoundlanders to "put Canada first, but don't ignore your provincial interests."

Wells said federal officials in Ottawa had sought to portray Newfoundland's holdout position as destroying the unity of Canada. He warned that if Ottawa continued to press him or threaten economic reprisals, "they may find a backlash in Newfoundland."

Prime Minister Brian Mulroney and other politicians had said that a new era in Canadian unity was forged in the seven days of marathon negotiations last week aimed at ending a growing constitutional crisis over language and culture conflicts.

Mulroney and the premiers of Canada's 10 provinces had come together in Ottawa to save an accord signed at Quebec's Meech Lake in 1987 and designed to bring predominantly French-speaking Quebec -- where separatist sentiment has repeatedly flared -- into Canada's 1982 constitution. But three English-speaking provinces had balked at ratifying the accord because they said it gave too much power to Quebec.

It appeared Saturday night that the crisis had been resolved with the signing of an expanded Meech Lake pact, but Wells said today it "did not address Newfoundland's concern to any acceptable degree."

Wells's determination to take the compromise package either to his legislature or the people of the province appeared to represent the greatest threat to constitutional reform aimed at persuading Quebec to sign Canada's constitution.

But even if Newfoundland affirms the pact by the June 23 deadline, it remained far from clear tonight how much the compromise agreement would ease Canada's underlying centrifugal forces of regionalism.

The leader of Quebec's separatist movement also condemned the constitutional amendments and vowed to intensify the French Canadians' struggle for political independence from the rest of the confederation.

A referendum in Newfoundland could spell doom for the shaky package because Newfoundland, which did not join the Canadian confederation until 1949, traditionally has felt more isolated and alienated from the rest of Canada than perhaps any other province. A public opinion poll last month showed that 52 percent of Newfoundlanders would reject the Meech Lake accord if a referendum were held, although 63 percent said they would back Wells's decision to approve it if he got the changes he wanted.

Wells angrily told reporters in the capital of St. John's that he never endorsed the constitutional reforms adopted at Meech Lake in 1987, or the compromise add-on provisions adopted in Ottawa Saturday night. He said the only thing he signed was an undertaking to endorse the accord if it received legislative approval in his province.

Many Newfoundlanders feel particularly hostile toward Quebec because the relatively wealthy province was given the right to exploit immensely profitable energy resources in Labrador, which is part of Newfoundland, while Newfoundland continues to depend on federal grants for 48 percent of its annual budget because of a depressed economy.

The effect of Saturday night's compromise on separatist feelings in Quebec may not be definitively measured for several weeks, and may depend largely on what happens to the expanded Meech Lake accord in Newfoundland. The premiers of the other two provinces that had objected to Meech Lake -- New Brunswick and Manitoba -- signed the new pact Saturday night and said they would push it through their legislatures by the June 23 deadline.

Jacques Parizeau, leader of the Parti Quebecois which led a failed independence referendum in Quebec in 1980, said the constitutional provision recognizing Quebec as a "distinct society" had been diluted by Saturday's compromise agreement.

At a news conference in Quebec City, Parizeau said the premiers' approval of a statement of clarification by constitutional lawyers on the effects of the "distinct society" provision "completely transformed" the constitutional amendments approved in 1987. The lawyers' statement says Canada's bill of rights is not infringed or denied by the "distinct society" clause, and that no new legislative powers have been conferred on Quebec.

While the Parti Quebecois is only a minority opposition party in the Liberal Party government of Quebec Premier Robert Bourassa, its views have reflected the sentiments of many Quebec nationalists.

If the Meech Lake accord and the parallel agreements reached in Ottawa Saturday night survive the June 23 deadline, Quebec is expected to sign the constitution.

In addition to adoption of the "distinct society" clause and other provisions of the original Meech Lake accord, the main elements of Saturday night's compromise are: The creation of a special parliamentary commission which will begin hearings in July into a new "Canada clause" for the constitution's preamble that would broaden the definition of the Canadian identity and explicitly recognize women's equal rights and the multicultural character of the country. Provision of a five-year deadline for the provincial premiers to reform the appointed Senate chamber of Parliament into an elected and more equally represented body. If the premiers fail to reach agreement, Senate seats would be redistributed automatically to give the sparsely populated western and Atlantic maritime provinces more representation.