The chairmen of key House and Senate committees, reserving judgment on the U.S.-Canada free trade agreement until they know more of its details, told administration officials yesterday to work with Congress to implement the pact.

"I want both the administration and the Canadian government to recognize that this is going to be a tough package to steer through the Congress," said House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) after an afternoon briefing by Treasury Secretary James A. Baker III and U.S. Trade Representative Clayton K. Yeutter.

"I will reserve judgment on my position until I have had time to fully analyze the agreement and hear from the numerous interests affected by its terms," he added.

Finance Committee Chairman Lloyd Bentsen (D-Tex.) also declined to commit himself to supporting the agreement, which was reached minutes before a midnight Saturday deadline, until he gets more details.

"But I'm delighted the two countries can get together because if we can truly achieve a free trade agreement that is truly beneficial to both sides, we'll see a substantial increase in jobs for both Canada and the United States. I think the consumer will be the big winner," he said after a morning briefing by administration officials.

The support of Bentsen and Rostenkowski is considered crucial for congressional approval of the agreement because many other lawmakers will follow their lead on this major trade issue.

But there were also suggestions from both House and Senate sources that the price of passage could be greater administration cooperation on other contentious issues -- especially a major trade bill now being worked on by a House-Senate conference committee and ways to cut the budget deficit.

"It can't help but interrelate. It will all end up in a bargain over trade and the budget. Canada is all part of the bargaining process," said one key congressional staff member.

"No one is going to be stampeded into doing this for this administration," he added, "but no one wants to kill the Canada deal."

Another Capitol Hill staff member, present at the briefing, said, "It was implicit that these issues are not self-contained."

Bentsen, however, strongly denied that he supports that kind of strategy. "I don't agree with that and I don't do that."

At the Finance Committee briefing, interrupted twice by roll call votes, Sen. George J. Mitchell (D-Maine), a former federal judge, questioned Baker and Yeutter about the dispute settlement procedures that substitute a tribunal with U.S. and Canadian members for the American or Canadian court systems.

"It's a new concept and there is a lot unclear," said Mitchell, whose constituents in Maine often have cross-border trade disputes with their Canadian neighbors. "I don't know enough to know if I will support it or not."

Sen. John C. Danforth (R-Mo.) also said he is "undecided" because of "several questions that need to be answered." Among them, he listed guaranteed compliance by Canada's 10 provinces, the exclusion of greater protection for intellectual property, and a better explanation of the meaning of Canada's "cultural sovereignty," which in a special provision excludes publishing, broadcasting and films from the pact.

{In Ottawa yesterday, Prime Minister Brian Mulroney said "everything is going fine" in his talks to gain the support of Canada's provincial premiers for the pact, the Dow Jones news agency reported.}

The ranking minority member of the Finance Committee, Sen. Robert Packwood (R-Ore.), and a key Democrat on the panel, Sen. Daniel Patrick Moynihan (N.Y.), came out fully in favor of the agreement.

Packwood, who reported that many businesses in Oregon will gain from provisions in the pact, said, "From what I have seen and heard so far ... we have a dynamite framework to build upon.

"I think this may be one of the most significant economic agreements that the United States has ever reached," he added.

Moynihan called the agreement "an enormous event" for the future of U.S.-Canadian relations and "a huge statement to the world" of how neighboring nations can cooperate on difficult issues. "I just hope we don't get lost in some of these tiny issues that are really transient," he said.

On the House side, Rep. Sander M. Levin (D-Mich.) said he supports the idea of an agreement, but raised questions as to whether provisions relating to automobiles make enough progress toward free trade.

Rep. Jim Leach (R-Iowa), though, called the agreement "a very artful compromise" that stands "in stark contrast to the protectionist fever sweeping Congress and most of the other legislative bodies of the world. I think it will be great for Canada, and very good for the United States."

Leaders of House and Senate committees are now concerned about making sure they have a voice in the drafting of the final agreement before it is signed and presented to Congress for approval.

Bentsen suggested that his committee's plate is so full that the administration might want to wait until next year before moving ahead, even though the fast track authority under which Congress would approve the bill without changes expires in January. Now that the process has started, Bentsen said the fast track remains in place despite the delay.