The Canadian Senate approved the historic U.S.-Canada free trade bill Friday, ending two years of negotiations and bitter political debate and clearing the way for a new trade relationship that could set the pace for freer trade around the world.

The upper chamber of Parliament, composed mainly of Liberal senators opposed to the trade pact, approved legislation implementing the agreement in a voice vote from which the Liberal senators abstained in order to let the legislation pass.The bill was scheduled to receive final approval later Friday from a Supreme Court judge representing Queen Elizabeth and takes effect Jan. 1. All legislation in Canada must receive formal royal assent before being enacted.

Liberal Sen. Ray Perrault told the Senate prior to voting the free trade agreement "represents one of the most important initiatives ever undertaken by Parliament. This is a momentous day."

But Perrault added that the lack of support in the upper chamber for the trade bill reflected the concern of a majority of Canadians over the impact of free trade and a closer relationship with the United States.

The Senate had previously refused to pass the legislation, forcing the Conservative government to hold a general election on Nov. 21. Although the Conservatives were re-elected with a majority of seats in the House of Commons, they won only 43 percent of the popular vote in the election. The Liberals and socialist New Democrats both opposed the trade agreement.

There was no special ceremony or fanfare to mark the parliamentary approval of the free trade bill, although some groups opposed to it have scheduled demonstrations in front of Parliament when the legislation takes effect Jan. 1.

Paul Peck, a spokesman for the External Affairs Department in Ottawa, said the only remaining step before the agreement takes effect would be an exchange of diplomatic notes between the two governments on Saturday.

"It's basically a low-key event. It's not being done with fanfare," Peck said, adding it was a difficult time of year to arrange any kind of ceremony.

The trade agreement, which will remove most tariffs to cross-border trade over a 10-year period and establish new trading rules between the two countries, has been hailed at various times by President Reagan and Prime Minister Brian Mulroney as a model for freer international trade.

Mulroney said the pact would ensure economic prosperity for Canadians and provide "a beacon of hope" for developing nations whose economies also depend on free trade.

Canada and the United States form the largest two-way trade relationship in the world, last year exchanging an estimated $160 billion in goods, about 75 percent of it free of tariffs that have been removed over the past decade.

On Jan. 1, tariffs will be eliminated on about 15 percent of bilateral trade affecting such products as computers, furs, fresh-frozen fish, animal feed and whisky.

On other products, tariffs will be reduced between 10 and 20 percent, then gradually phased out over the next ten years.

At the same time, it will be easier for professionals and service people to cross the border and work on a temporary basis in the other country.

The two countries are expected to announce in January the formation of a unique bilateral tribunal to hear trade-related disputes.