Chief Justice Warren E. Burger asked Congress today to create a new national appeals court to relieve the Supreme Court of as many as one-third of its cases.

Although the new panel's jurisdiction would be limited, its decisions would be binding on the entire country unless overruled by the Supreme Court, Burger said. Such a court would represent the most fundamental alteration of the federal judicial system in nearly a century.

In his annual State of the Judiciary speech to the American Bar Association convention here, Burger said a dramatic restructuring is necessary to "avoid a breakdown of the system--or of some of the justices."

In comments earlier, Burger used even stronger terms: "We are approaching a disaster area, not just a problem . . . . We've got 90 to 100 cases filed every week. I have been surprised that we haven't had a breakdown of the system, to say nothing of a physical breakdown of some of the justices with the work load."

"Sixty hours a week minimum, 70 and 80 to some extent, isn't a very good diet for human beings, especially when they get beyond 40, as most of us are now," he said. Five of the nine justices are over 70 years old.

Similar ideas for a new intermediate court have been discussed since the case load problem was widely recognized a decade ago. But today was the first time the chief justice has put his influence behind a specific solution.

His speech came after seven months of renewed public debate among Supreme Court justices and in the legal profession about the problem, which reached record proportions last year when the high court received 5,300 case filings.

That was the most in a single term and nearly four times the number handled by the nine justices 30 years ago.

The justices, generally with substantial help from their law clerks, chose about 150 of the 5,300 cases for full decisions and opinions. Under Burger's proposal, between 30 and 50 of those rulings would be made by the new panel, which would form a new judicial level between the Supreme Court and the 12 U.S. circuit courts of appeal.

When two or more of those appellate courts disagreed on an issue, the panel would resolve the conflict. Burger suggested it also could handle some cases involving interpretations of acts of Congress, although he was not specific.

The assumption of such proposals for intermediate courts is that the justices often grant review not because of a case's importance but to bring uniformity to the law by resolving "intercircuit conflicts."

Critics have suggested that such a panel simply would create another layer of judicial bureaucracy with cases finding their way to the Supreme Court just as they do now. But Burger said he "would have confidence" that the panel could resolve conflicts "in such a way that the Supreme Court would not often find it necessary to grant further review."

"It will no longer do to say glibly, as some have, that we do not need 'another tier of courts,' or another court or a change," he said. " . . . That is meaningless in terms of the needs of the present, and particularly of the next 10 to 20 years and for the 21st century. We can no longer tolerate the vacuous notion that we can get along with the present structure 'because we have always done it that way.' "

Burger said the new court would be an "interim" measure lasting five years, after which a permanent solution would be considered. The judges would be designated from a pool of 26 existing judges--two from each circuit and two from the Court of Appeals for the Federal Circuit in Washington. They would sit on a rotating basis in panels of seven or nine members.

Burger did not say who he thought should select the panel members.

Burger said a "clear majority" of the Supreme Court is "essentially of one mind: that there is indeed a very grave problem and that something must be done." Burger was referring to speeches by seven of the justices in the last few months including a controversial proposal made last summer by Justice John Paul Stevens under which the Supreme Court would divest itself of its authority to select cases it reviews and transfer that responsibility to a new court. Burger and other justices who have spoken are known to oppose that idea.

The court's newest member, Sandra Day O'Connor, also said here today that statistics "make it clear that action is needed" to stem the "tide" of cases in federal courts at all levels.