United Press International yesterday withheld publication of an article on what had earlier been described as an advance copy of a Supreme Court opinion.

UPI Supreme Court correspondent Elizabeth Olson, responding to questions Friday about rumors that an opinion had leaked before the date of issuance, had said that a story about the opinion would be filed by the wire service for Sunday publication.

But yesterday Grant Dillman, UPI vice president and Washington manager, said in a statement that the wire service had been "so far unable to establish the authenticity" of the "document" it had obtained "suggesting the way the court would rule" in an important sex discrimination case.

The case, The County of Washington v. Alberta Gunther , involves an interpretation of laws requiring equal pay for women.

The Supreme Court's opinions are ordinarily kept secret until the moment the justices announce them from the bench. There have been several leaks in the past few years, each one causing a controversy about court security and a hunt for a source by Chief Justice Warren Burger.

Barrett McGurn, a spokesman for Burger, said that he was "pleased" with UPI's decision. McGurn was asked whether he or the chief justice had communicated with UPI after a story about the "document" appeared in yesterday's editions of The Washington Post. "I can't go into that," McGurn said.