The Supreme Court yesterday broadened the powers of federal regulators to protect the pensions of millions of American workers by affirming the government's authority to order corporations to reinstate terminated retirement plans.

The 8 to 1 decision in a case involving the LTV Corp. averted a potential financial crisis for the Pension Benefit Guaranty Corp., which insures $1 trillion in private pension benefits for 40 million workers much the way the Federal Deposit Insurance Corp. insures bank deposits. The ruling will make it harder, if not impossible, for corporations to use bankruptcy laws to "dump" their underfunded pension liabilities on the agency so they can have more cash for their creditors.

"This removes a major cloud that's been hanging over the agency for two and a half years," said James B. Lockhart, PBGC executive director. "The nation's retirees won a big victory today." He said the ruling in PBGC v. LTV should "send a strong message to all companies that they better not terminate their {pension} plans unless there is a financial need."

If the court had ruled against the PBGC, the agency would have had to assume $2 billion in LTV's pension liabilities and the door would have been opened for it to assume responsibility for other financially troubled companies in the future.

Lockhart has said at least a half dozen other companies on the edge of bankruptcy might have tried the same tactic. The fund has $3.2 billion in assets and liabilities of $4.2 billion.

LTV, a Dallas-based steel and aerospace manufacturing company, announced four years ago it could no longer fund its pension plans after filing for bankruptcy, leaving the PBGC with the financial liability for its 60,000 retirees. The promised benefits under the three pension plans involved exceeded the assets of the LTV retirement funds by $2.3 billion.

When the agency took over the LTV pensions, it did not pay the same level of benefits that retirees and active employees would have received under the original plan. The United Steelworkers union threatened to strike unless the company made up the lost benefits and LTV then negotiated what are called "follow-on" plans that made up for most of the lost benefits. The arrangement allowed LTV to pay approximately $75 million a year in pension benefits while the PBGC was forced to pay $400 million a year.

By the time the agreements were reached with the union, the steel industry and LTV had made a dramatic financial turnaround and PBGC ordered the company to asssume responsibility again for the pension plans.

LTV refused to take back the plans and challenged the right of the agency to make it. Both a federal district judge and a U.S. Court of Appeals sided with LTV.

In an opinion written by Justice Harry A. Blackmun, however, the court said it is "eminently reasonable" for the PBGC to prohibit companies from setting up extra pension benefits for its employees after it had turned the bulk of the cost of its plans over to the government.

Justice John Paul Stevens dissented. He argued that as long as LTV was making its best effort to reorganize and emerge from bankruptcy the PBGC had no business interfering with managerial decisions made by the company and the bankruptcy court.

Lockhart said yesterday the PBGC would immediately begin work with LTV to return the pension plans to the company. He said LTV's liabilities for the return would be in the "hundreds of millions of dollars," but added that the company has "$1 billion in cash right now."

LTV said it could not afford to take back the pension liabilities. In a brief statement issued after the ruling the company said:

"LTV filed for Chapter 11 {voluntary bankruptcy} protection four years ago because among other things we could not afford to make payments into these three pension plans. That situation has not changed. We still cannot afford the plans. It will be the company's objective to continue to seek the resolution which recognizes this fact."

The company will either have to persuade the steelworkers to renegotiate their benefits or convince the PBGC that it still cannot afford the pension plans and should be allowed to terminate them again. Lockhart said he would oppose that.

Another option would be to deprive its creditors and stockholders so it can pay the pension costs. Steel industry analyst John C. Tumazos of Donaldson, Lufkin and Jenrette said "the decision means LTV will be forced to pay its pension obligation rather than make payments to unsecured creditors or have money left over for the stockholders."