Congress tailoring massive trade bill to avoid Reagan veto. Long-awaited measure seeks to reverse trend of big overseas deficits

The US Congress stands poised to change the rules of the global marketplace. This week, lawmakers are supposed to put final touches on the most sweeping trade legislation Congress has ever considered. The massive piece of legislation overhauls the nation's trading laws and intends to help slim the bulging US trade deficit.

The bill is supposed to be ``tough,'' but not ``protectionist.'' It is supposed to put the world on notice that the United States will not stand idle while its trading partners erect stiff import barriers; but it is not supposed to provoke a trade war.

Perhaps trickiest of all, it is not supposed to trigger a presidential veto.

``I can tell you one thing: it has not been easy,'' says Sen. Lloyd Bentsen (D) of Texas, chairman of the Senate Finance Committee, and a leading figure in the congressional trade deliberations.

The scope of the undertaking suggests the difficulty of the task before Congress. The House of Representatives and the Senate each labored for three years to produce separate bills - elaborate, 1,000-page affairs that cover everything from worker training to lamb imports.

No fewer than 199 members of Congress - roughly two-fifths of the 535 members of the House and Senate - have organized themselves into 17 House-Senate committees charged with reconciling innumerable differences between the two versions. Those committees have been meeting for the last three months to come up with one piece of legislation ready for the President's signature.

It is a high-stakes endeavor. Last year's trade deficit topped $171 billion. Accumulated US debts to the rest of the world are said to weigh heavily on the national economy - costing jobs, slowing growth, and generally diminishing prospects for future prosperity.

Responding to that threat, lawmakers have taken to trade issues with a vengeance. ``That's made the trade bill negotiations even messier than they might have been,'' says Rep. Bill Frenzel (R) of Minnesota.

Now, the effort to rewrite US trade law has shifted into high gear. House Speaker Jim Wright (D) of Texas, who put the trade bill at the top of the Democrats' ``to-do'' list for the 100th Congress, had told the 17 committees to come together with their compromises by Wednesday. That deadline, like so many of the self-imposed timetables Congress toils under, has been quietly forgotten. But the trade bill conferees are under pressure to wrap things up by the end of the week or, at least, have a package ready for a final vote in the House and Senate shortly after Easter.

Scores of amendments have already been dropped. The measure curbing lamb imports, for instance, was trimmed from the list. But in classic fashion, lawmakers have saved the hardest bargaining for last.

It is not clear, for example, whether the trade bill will include provisions aimed at improving the troubled US system for keeping state-of-the-art technology out of the hands of the Soviet military. Both chambers included such provisions in their trade bills. But a Senate-passed provision to punish Norway's Kongsberg Vaapenfabrikk and Japan's Toshiba Corporation for their subsidiaries' illegal sales of strategic equipment to the Soviet Union has met with stiff resistance from House negotiators and the Reagan administration.

Both object to mandatory sanctions, arguing they undermine efforts to strengthen the international system of technology transfer controls under the Coordinating Committee for Multilateral Export Controls. Reagan administration officials say that the penalties, if included in the trade bill, would provoke a presidential veto.

But Sen. Jake Garn (R) of Utah refuses to give up the sanctions. And Senate supporters of the Garn position have tied the fate of revisions in US export-control law to the Toshiba case.

``I just don't know how it will work out,'' says Rep. Don Bonker (D) of Washington, who heads the group of House negotiators on the issue.

Still to be formally settled is the fate of the most conspicuous amendment in the House bill, the provision - authored by Rep. Richard Gephardt (D) of Missouri - that targets certain nations for mandatory US retaliation for unfair foreign trading practices. It is virtually certain that the amendment will be abandoned in favor of a Senate proposal that calls for more selective retaliation against countries whose trade practices are conventionally defined as ``unfair.''

With Gephardt's withdrawal from the presidential race, says one House Democrat, ``the amendment's gone'' and so, too, is the provision that trade bill critics most often cited as protectionist.