Trade Accord Supporters Confident of Senate Approval : GATT: Senators are reported lining up behind the landmark global pact. Unusual alliances, familiar arguments precede today’s vote.

The Senate began debate Wednesday on a landmark reduction of tariffs and other barriers to world trade as supporters, including senior Clinton Administration officials, declared that the final votes for passage are falling into line.

One survey showed just enough senators supporting or leaning toward supporting the pact for the Administration to succeed--a comfortable position with 24 hours to go, especially with more votes possible from 15 to 20 senators who remain undecided.

“We do expect that by the time the vote is cast tomorrow, we will have the votes,” White House Press Secretary Dee Dee Myers said.

“I feel a little like a coach at halftime when you’re ahead--but you’ve got the second half yet to go. . . . “ said Treasury Secretary Lloyd Bentsen. “The momentum is swinging our way.”

With the House having approved the accord that would vastly expand the General Agreement on Tariffs and Trade, which has governed global commerce since 1947, the Senate ballot today is the final step in a process so long in the making that it has spanned three presidencies.

The fruit of seven years of negotiations that began during the Ronald Reagan Administration, the pact ultimately would have 124 nations agree to slash tariffs, the taxes charged on imports, by roughly 40% and bring down other barriers to global trade.

It would force participants to cut subsidies to farmers, expanding the market for U.S. agriculture, widen copyright protections for computer software, videos and recordings that are heavily pirated, and begin to make it easier for financial firms, among them accounting offices and insurance companies, to do business beyond their home markets.

All told, the Administration has claimed, it would cut tariffs by nearly $750 billion around the world, a shift that would lower prices and encourage greater consumption. Administration officials have also said that it would boost the U.S. economy by as much as $200 billion a year--a figure even other supporters label as overly optimistic.

From early-morning appearances on television news programs to speech-making on the Senate floor well after sunset, supporters and opponents rehashed the by-now familiar arguments. The debate sliced oddly across the political landscape, uniting common foes and driving wedges between longtime allies.

To demonstrate appeal that stretched across the spectrum, a business and agriculture alliance supporting the agreement brought together a group ranging from Sen. Barbara A. Mikulski (D-Md.), one of the Senate’s most liberal members and a trade protectionist, and such western conservatives as Sen. Alan K. Simpson (R-Wyo.) and Sen. Robert F. Bennett (R-Utah).

Each offered strong backing for the pact as a measure that would create jobs by expanding exports. California’s two senators, Dianne Feinstein and Barbara Boxer, also joined the coalition.

Yet ideological allies found themselves on opposite sides, as illustrated by Sen. Howard M. Metzenbaum (D-Ohio) and Mikulski, who supported the accord while defending her past support for protectionist measures.

Mikulski said that her “heart and my soul” remain with “the blue-collar community” of Baltimore that traditionally has opposed free-trade measures. The trade pact, she said, would add jobs.

“I’m going to go GATT because I’m absolutely convinced (that) the old ways are not working . . . and a new economy is about to be born,” Mikulski said. “The only way the United States will be able to continue as a world economic power is to go GATT.”

Metzenbaum, who is retiring, said that the trade pact would limit the United States’ ability to ban foreign goods made by children and held up pictures of children at work.

“Around the world today, as many as 200 million children are subjected to abusive labor practices in sweat shops, in mines, in factories and in the fields,” he said. “Global trade may bring great riches to multinational corporations but for millions of children around the world it is an unmitigated disaster.”

At issue are concerns that U.S. laws prohibiting the sale of foreign products made without regard to workers’ rights or danger to the environment could be declared by international authorities under the new World Trade Organization, which would be created by the pact, to be unfair restraints on trade.

Administration officials said that the new body would have no authority to overrule U.S. laws. In an agreement that secured the crucial support of the expected next Senate majority leader, Bob Dole (R-Kan.), the Congress could vote to end the nation’s participation if a panel of U.S. judges finds that the international rulings are consistently unfair to the United States.

“We have a safety net,” Boxer said. “If it doesn’t work right, we can get out.”

Even as the anticipated support count neared the 60 votes needed to waive Senate budget rules and move the legislation forward, the Administration pressed wavering senators to climb aboard.

Clinton invited about 20, many of them undecided, to a breakfast today at the White House, and Bentsen, U.S. Trade Representative Mickey Kantor and other senior officials corralled senators in person and on the telephone to nail down their support.

A survey by the Associated Press found 60 senators declared in favor of the trade plan or leaning toward supporting it, 26 against it or leaning against it and 14 undecided. A trade official said that about 20 senators remained uncommitted.