OTTAWA, OCT. 4 -- Canadians waited nervously today to learn the details of the trade agreement that Prime Minister Brian Mulroney has reached with the Americans, asking whether the former labor lawyer had shrewdly forced U.S. officials to make important concessions or been stampeded into a "desperation deal."

Few here were willing to take a firm position on the outcome until they read the fine print. Even left-wing New Democratic Party leader Ed Broadbent, who had opposed the trade negotiations from the beginning was hedging his bets.

"Jobs are at stake, our culture is at stake, our very sovereignty is at stake," said Broadbent, currently Canada's most popular national leader, alluding to past criticisms. But he added to his standard remarks that "we have to see the details before deciding if it is a positive deal."

Canadians are dependent on exports to the United States for their national prosperity and could be seriously harmed economically if there was no accommodation with the protectionist forces in the U.S. Congress. On the other hand, Canadians worry that a trade pact might find Canada swallowed up by the colossus to the south and forced to adhere to its social and cultural policies.

"Brian Mulroney's 'Free Trade' Could Cost Us Canada," says one version of billboards that have been put up by labor unions and cultural nationalists.

For Mulroney, who has made the trade initiative the centerpiece of his economic and foreign policy, the stakes are high. If the deal is perceived here as a sellout, there would appear to be little prospect of improving his current low public rating in polls. Mulroney is weak politically, the consequence of his government being tarnished by a long string of small scandals.

A few days ago, Mulroney told reporters his neck was on the line.

Early this morning, nearly two hours after the deal had been announced in Washington and the news had been broadcast on the transistor radios of reporters waiting outside his office, a wan and drawn Mulroney emerged with key Cabinet advisers.

"I'm feeling a little bit better about my neck right now," he said.

Mulroney told a television interviewer tonight that the pact would boost Canada's economy, creating 350,000 new jobs.

"Unquestionably there will be areas of disruption in the country," he said, but he minimized the potential ill-effects. He indicated that he might consider changes in the draft agreement if the American negotiators felt they were esssential to sell the deal on Capitol Hill.

When asked earlier about Canadians' concerns that current advantages in the automobile trade had been reduced in the agreement, Mulroney replied: "I think that if you wait and see the agreement, then you'll be satisfied -- I think -- with any changes we made anywhere consistent with the objectives we set out."

Trade opponents led by Canada's militant unions are strong and have spent months gearing up to oppose any deal. Business firms and financial institutions that say an agreement is needed to ensure security of access to the American market chafe when asked whether that means they are willing to consent to changes that would expose them to greater competition.

As the deadline for negotiations neared, public support for a deal seemed to evaporate and nationalistic outbursts multiplied. A walkout by Canadian negotiators was applauded here. Also popular was Mulroney's hang-tough public stance, while U.S. Treasury Secretary James A. Baker III appeared in Canadian eyes to be ardently wooing Canadians back to the bargaining table.

But Canadians still fretted aloud that the Americans always tended to take them for granted. It was news on the Canadian networks that the American networks were giving the down-to-the-wire negotiations scant attention.

The rapid pace of the bargaining in the end, however, also worried many. The headline on the lead editorial of the weekend edition of the Montreal Gazette cautioned, "Don't be stampeded."

The Toronto Globe and Mail warned against any deal that would force Canada to eliminate its generous grants and subsidies. "We support free trade," it said, "but free trade or no, Canada will never buy what the Americans are hawking to the civilized world as social policy."