Navy women for the first time would be allowed to land planes on carriers and serve temporarily on fighting ships under a proposal just approved by the Pentagon's new leadership.

Defense Secretary Harold Brown and Navy Secretary W. Graham Claytor Jr. are recommending to the White House that the law banning women from warships be changed, a proposal President Carter is expected to endorse and forward to Congress soon.

If the proposal goes forward to Congress as anticipated, the lawmakers will be caught between traditionalists, who do not want women to go to sea, and equal rights advocates, who contend it is high time the ban was lifted.

Former Navy Secretary J. William Middendorf allied himself with the traditionalists and bottled up a similar liberalizing proposals last year. But Claytor, a former Navy officer, as was Middendorf, took an opposite view and made changing the law a top priority objective since taking office last month.

Claytor's push for a larger role for women in the military is part of the growing conviction among Pentagon executives that the most promising answer to filling the ranks of the services with volunteers is accepting more women.

"It doesn't make any sense to talk about returning to the draft," said one Pentagon manpower executives, "at the same time recruiting stations are turning away highly qualified women.

This argument is now confronting politicians who are calling for a return to the draft on the grounds that the Army, Navy and Marine Corps cannot fill their ranks with high-quality volunteers.

A group of Navy women officers already has filed a suit in U.S. District Court to nullify as unconstitutional the 1948 law which states "women may not be assigned to duty in aircraft that are engaged in combat missions nor may they be assigned to duty on vessels of the Navy other than hospital ships and transports."

That law has been intepreted by Pentagon lawyers as forbidding Navy women pilots from landing on carriers even in peacetime or serving on warships even temporarily to meet training requirements of specific jobs.

The change advocated by Brown and Claytor would delete that restrictive sentence of the law and substitute language that would allow women to serve temporarily on warships not in combat and fill full-time jobs on research, and oceangraphic ships as well as transports.

Claytor, in the draft of the argument he has already prepared for Congress, said allowing women to serve temporarily - as opposed to tours of several months - on any ship not on a combat mission "would provide the Navy and Marine Corps with greater flexibility in the assignment of women,"

The Navy, under the more liberal policy, Claytor added, could "take fuller advantage of the talent available in its female resources . . . Experience to date indicated that sea service women are highly motivated, dedicated and very capable."

In a related development buttressing the case for widening opportunities for women in the military, the Pentagon has just finished a study which indicates that women cope with military duty better than their male counterparts.

In analyzing how many enlisted men and women dropped out of the service before completing two years, the Pentagon found that 29.1 per cent of the men who enlisted in fiscal 1974 dropped out, compared with 28.7 of the women.

This represented for women a sharp reversal of the dropout trend. Of all the women who enlisted in the services in fiscal 1971, the study showed, 40.8 per cent left the service for various reasons before completing two years.

The new policy, which allows women to stay in the service and rear children, was cited by manpower specialists as one reason for the turnaround. Another reason offered was that women entering the service these days are better qualified and more highly motivated than male volunteers.