WASHINGTON (AP) _ The Navy, hoping to shake a reputation for tolerating sexual harassment, said Wednesday that first-time Navy or Marine Corps violators of certain anti- harassment rules will automatically be kicked out of the service.

The Navy has been rocked in recent years by a series of highly publicized incidents of sexual harassment and abuse.

Last November an admiral was fired from a prestigious job after he failed to act promptly on a complaint by a female aide that she was sexually harassed at a Las Vegas convention of naval aviators. In 1989 a female midshipman at the U.S. Naval Academy was chained to a urinal and photographed by male midshipmen.

In an all-hands message transmitted on Tuesday, Adm. Frank B. Kelso II, the Chief of Naval Operations, said the tighter behavior standard would take effect March 1. The Navy made a copy of the message available to the news media Wednesday.

Jean Appleby Jackson, chairwoman of a Pentagon advisory group on women's issues, said, ''I'm encouraged they're taking a new approach. It sounds real encouraging.

''It's the kind of problem that's hard to get at unless you take firm approaches to it,'' Ms. Jackson, head of the Defense Advisory Committee on Women in the Services, said in an interview.

Kelso equated the problem of sexual harassment with the Navy's past internal battles against racial discrimination and drug abuse, saying it ''demeans victims and tarnishes our reputation as fair, hardworking professionals.''

Kelso wrote that the problem persists despite longstanding efforts to end it.

The new Navy policy states that members of the Navy and Marine Corps will be fired outright ''on the first substantiated incident'' involving the following circumstances:

-Threats or attempts to influence another's career or job to obtain sexual favors.

-Offering rewards in exchange for sexual favors.

-Physical contact of a sexual nature which, if charged as a violation of the Uniform Code of Military Justice, could result in punitive discharge.

The specific circumstances that would call for automatic dismissal on a first offense were spelled out in a Feb. 5 memorandum from Navy Secretary H. Lawrence Garrett III to Kelso and Gen. Carl Mundy Jr., the commandant of the Marine Corps.

''An incident is substantiated if there has been a court-martial conviction or the commanding officer determines that sexual harassment has occurred,'' Garrett wrote.

A service member would retain the legal right to contest his or her dismissal.

Lt. Mary Hanson, a Navy spokeswoman, said that until now commanders had the option of dismissing the most serious violators of anti-harassment rules, but dismissal was not required.

''These are additional, logical steps to make sure we're doing everything we can to eradicate sexual harassment'' from the Navy and Marine Corps, Ms. Hanson said.

In his all-hands message, Kelso said that repeat violators of ''less aggravated acts of sexual harassment'' may also be subject to dismissal.

Kelso said he also was ordering that sexual harassment training for sailors and marines be improved and made more widely available.