Reporting that some lawyers "don't know how to try a lawsuit," a special committee of the federal judiciary recommended yesterday that all new attorneys be required to pass a special test and gain trial experience elsewhere before being allowed to take cases in the U.S. courts.

"There is a need to improve the quality of advocacy in the United States district courts and this can best be accomplished by assuring minimum uniform national standards of competasy for admission to practice," the committee concluded after a two-year study.

It made its report to Chief Justice Warren E. Burger, who has been pushing lawyers to improve their trial ability and to the annual meeting of the Judicial Conference of the United States, which appointed the committee.

The committee, headed by Chief Judge Edward J. Devitt of the U.S. District Court in St. Paul, Minn., said it will spend the next year taking its recommendations to judges, lawyers, legal educators and law students around the country before submitting a final report.

The recommendations have to be approved by the Judicial Conference. All 96 U.S. district courts would then be urged to incorporate the recommendations in their own rules.

Devitt said it could be as long as two years before the first federal bar exam would be given. These exams would apply only to new lawyers; those already admitted to practice in federal courts would not have to take the test.

The long-term result, Devitt said, would be to improve the way Americans are represented by lawyers in all the courts -federal, state and local.

The committee cited studies showing that both judges and experienced lawyers believe that attorneys fail to do a "good" job in one of four cases in the federal courts.

The committee's recommendations are the most specific made by a high-level group - composed of lawyers, judges and legal educators with five law students as consultants - toward solving the problem of improving the quality of the lawyers who practice in the nation's courts.

Before being allowed to practice in a federal court, the committee said, a lawyer should show, through a test, minimum knowledge of the rules of federal courts - including jurisdiction, rules of procedure in civil and criminal cases and for appeals, rules of evidence, and the code of professional responsibility.

"The applicant should show some minimum evidence of ability to try a lawsuit competently before being permitted to do so," the committee said.

In addition, the committee said lawyers should gain experience in four trials before taking a case alone in the federal court. This experience could include watching federal court cases under the supervision of an experienced lawyer; working with another lawyer, or taking part in simulated trials in law school.

At least two of the four chances to gain experience should be in actual trials, which could be in state or local courts, the committee said.

In a recommendation that could affect lawyers currently practing in federal courts, the committee said each district court should appoint a "performance review committee" of experienced local lawyers to help attorneys who fail to do a good job in trials.

Devitt said the committee was split over whether to include nonlawyers on the performance review board.

The committee also suggested that law schools spend more time training trial attorneys and recommended that federal courts allow students in special programs, working under an experienced attorney, to try cases in the U.S. courts. These cases would count toward the needed trial experience.

The Judicial Conference is the policymaking body of the federal judicial system. It is headed by the chief justice and includes the heads of the 11 federal appeals courts and representatives from each of the district court circuits.