U.S. District Court Senior Judge John J. Sirica ruled yesterday that it is unconstitutional for Congress to flatly bar women from serving on U.S. Navy ships.

Instead, he said, it should be up to the Navy to assign its personnel - men and women alike - as it sees fit.

He made it clear that there may be additional "unanswered questions" about the effects of full sexual integration that might lead to Navy to continue its policy of discrimination in certain areas, such as combat vehicles, or to wait until it reequips certain ships before allowing women to serve on them.

"Those are essentially military decisions that are entrusted to executive authorities and the court expresses no view whatever on what their outcome should be," Sirica said.

"But what the court is requiring is that executive authorities move forward in measured steps to approach these issues . . .," Sirica added.

Sirica ruled in a suit brought by four Navy women who said the Navy was discriminating against them and 21,800 other Navy women who were prohibited by federal statute from serving aboard Navy ships other than transport and hospital vessels.

Because there are no Navy hospital or transport ships in operation now, the women were effectively precluded from any ocean duty as crew members, they said.

The Navy said it was merely following Congress's mandate when, 30 years ago, that body passed the statute blocking the assignment of females to ships.

He said, however, that this case "makes amply clear over a generation later" that Congress was wrong when it passed the total bar to women serving on ships.

"It acted without serious deliberation, against the expressed judgment of the military, and by foreclosing the Navy's disrection regarding women well beyond the legitimate demands of military preparedness and efficiency, it acted arbitrarily," Sirica said.

The women who filed the suit said their inability to be assigned to sea duty blocked them from entering or advancing in various Navy fields of expertise.

Yona Owens, of Arlington, one of the plaintiffs, is an "interior communication electrician," for example. Her job, according to court papers, involves repairing and maintaining sophisticated electrical equipment primarily used for navigation and found aboard ships. She requested a shipboard assignment to develop and use her skills more fully.

However, the Navy has refused to even consier her for duty "irrespective of her personal qualifications" Sirica pointed out. Similar complaints were raised by the other three women named in the suit who could not get assignments solely because they are females.

Sirica said that in recent years there has been a marked increase in the recruitment of women in the military and a heavier reliance on women to fill a wide range of military jobs.

"Significantly, none of the limitations and disadvantages facing Navy women is traceable to any studied evaluation made of male and female capabilities that reveals that women lack the native ability to perform competently in positions held exclusively by men," he said, adding that several military reports suggest "that just the opposite is true" in some cases.

The judge also said the Navy could benefit financially by increasing the range of jobs that women could perform in the service. For example, he said, high quality women can be recruited much more cheaply than men of equal quality for the same jobs.

Sirica reiterated that the issue in the case was not whether the naval forces should be completely integrated and the roles of male and female members made perfectly equal, but whether Navy women should have the same rights as men to receive assignments aboard Navy ships.

The Navy has supported the ability to have more discretion in the assignment of women aboard ships, and a bill is pending in Congress to that effect with top Naval support.