PHILADELPHIA — Reversing her earlier decision, a federal judge ruled that companies may offer younger retirees better healthcare benefits than they give older retirees who qualify for Medicare.

The AARP sued over the rule change proposed by the Equal Employment Opportunity Commission on grounds that unequal health packages amount to age discrimination.

U.S. District Judge Anita B. Brody initially agreed, granting an injunction in March that barred the federal agency from adopting the rule. However, a recent U.S. Supreme Court ruling in an unrelated case compelled her to change course, she said in a ruling Tuesday.

Brody prohibited the agency from acting, though, until the AARP has a chance to appeal.

A lawyer for the AARP, which sued on behalf of several members who saw their health benefits decline when they turned 65, said an appeal is likely.

EEOC Chairwoman Cari M. Dominguez said yesterday the rule change is in the public's interest, arguing that employers might otherwise eliminate retiree health benefits altogether.

The AARP questions that assumption.

"There are so many factors driving employers away from retiree health benefits ... escalating health costs, demographics; all sorts of things influence employers' decisions," AARP Foundation attorney Laurie McCann said.

The EEOC exemption would let employers cut health benefits for older retirees while offering no guarantees to younger employees, McCann said.

Some large employers and unions support two-tier benefit plans, saying that younger retirees need more generous bridge policies until they are eligible for Medicare, the federal program that provides health benefits for more than 40 million older and disabled Americans.

"We think that retirees of all ages could end up, inadvertently, having a reduction or loss of benefits if the AARP position were to prevail," said Paul Dennett, a vice president at the American Benefits Council, which represents many large U.S. companies.

Between 10 million and 15 million retirees receive health-care coverage from former employers. Of those, between 3 million and 4 million are under age 65.

Brody initially ruled that companies, to comply with federal age-discrimination laws, could offer separate packages only if they were of equal value or provided equal benefits.

Then Supreme Court Justice Clarence Thomas — in an Internet access case known as the "Brand X" case — said in June that judges should generally defer to the expertise of federal agencies.

Brody said Tuesday she must therefore uphold the EEOC's request to depart from the equal value or equal benefit standard of the Age Discrimination in Employment Act.