Florence Tate said yeterday that she plans to resign as press secretary to District of Columbia Mayor Marion Barry at the end of next month to become an American representative for African guerrilla leader Jonas Savimbi and his National Union for the Total independence of Angola (Unita).

Tate, 48, will be the first high ranking Barry appointee to voluntarily quit the year-old administration.

"I of course continue to support the mayor and the administration and his program. No difference between me and the mayor forced me to resign," she said in a brief telephone interview yesterday."Resuming work for UNITA is something that has been important to me for a long time."

Barry's office issued only a terse statement on the resignation. "The mayor has not received a letter of resignation from Florence Tate," the statement read. "Mrs. Tate is out sick today and will return to work tomorrow morning."

Several Barry aides and friends of Tate agreed yesterday that she had not been forced out of the administration. But, they said, Tate had for months held differing views with Barry over general administration policy toward the news media.

She disagreed with Barry's frequently defensive and personalized posture toward the press, they said, and also disliked the way in which he handled publicity of several matters, including the purchase of his new home. Tate's performance also was handicapped, the sources said, by being excluded from the mayor's inner circle since the early days of the administration.

"She never recovered from having to lower her expectations of what the job would be," one Barry aide said recently. "It was at that early point that she lessened her resolve to stay two or three years."

Tate, a former reporter for the Dayton Daily News, former media coordinator for the National Urban Coalition and enthusiastic publicist for liberation movements in southern Africa, joined the administation after working as a volunteer in Barry's longshot campaign for mayor. Her official title was press secretary and public relations adviser.

If there was anyone who best typified the trendy amalgam of black nationalism and newly affluent style of the new generation of middle-class blacks that Barry brought into city hall, it was Florence Tate.

She decorated her office with a blend of butcher-block hardwoods and African artifacts. Just before the mayor's inauguration, she filled the basement of her house on Roxanna Road NW off upper 16th Street with dozens of up-and-coming black lawyers, journalists, entrepreneurs and politicians -- including the mayor-elect -- for a nostalgic "dashiki party."

Tate took over the $38,184-a-year job in January and immediately transformed widespread general excitement over a new administration in the nation's capital into a string of laudatory stories about Barry in national and international magazines.

While she was often ill at ease with the intricacies of the bureaucracy, she often pressed Barry for answers on tough issues, called reporters at all hours of the day alert them to important news events or stories that would make Barry look good. She seldom offered "no comment" responses.

From the early days of the administration, Tate urged Barry for a more open attitude toward the news media, sources said. She tried to assure him that articles critical of him were in no way personally motivated and often argued that voluntary disclosures would avoid unnecessarily embrassing exposes, according to the sources.

Tate was seldom included in discussion of key matters, one source said, and often first heard of mayoral decisions when reporters asked for an official response. Some insiders considered her view on press relations to be diametrically opposed to that of Barry's sometimes feisty top adviser, general assistant Ivanhoe Donaldson.

"She believed in frank and open discussion and free flow of information. He didn't. He prevailed on that," one Barry aide said yesterday.

Tate was also said to have been up set because she was not consulted in advance about how the terms of Barry's purchase of a new home should be handled in the press, and on his apparently inaccurate representation of his wife's salary to a reporter.

It was Tate who last year asked the mayor to allow a reporter to ride with him after a record city snowfall. An account of Barry's statements during that ride resulted in the first overwhelming criticism of his management of city government.

Tate's Letter-to-the-Editor response, which began with the single-word paragraph, "Uncle!" assured readers that "Mayor Barry loves this city and its people" including the reporter who wrote the story.

"However, the mayor will probably never give him another lift, certainly not at the instigation of the press secretary," she wrote.

In a Dec. 23 letter to The Washington Post, she accused columnist richard Cohen, a frequent critic of Bary, of having "something personal against the mayor."

"C'mon, Richard," she wrote, "Either 'fess up to what's really bugging you about marion Barry, or give us all a break, man."