WASHINGTON (AP) _ Princess Diana arrived amid no pomp and awkward circumstances.

The princess slipped quietly into Washington late Thursday afternoon to visit the Brazilian ambassador and his wife. The trip takes Diana far from the hullabaloo at home over the details of her disintegrated marriage.

She is expected to stay through the weekend, when more sure-to-be- embarrassing excerpts of an authorized biography of her husband, Prince Charles, will be published in London's Sunday Times.

Diana will stay at the residence of Ambassador Paulo Tarso Flecha de Lima and his wife, Lucia, in Washington's diplomatic row. Mrs. de Lima and the princess have been friends since the ambassador's previous assignment in London.

The princess flew into New York from London on Wednesday, met Mrs. de Lima there and spent the night in a Manhattan hotel.

The State Department is helping with security, but no official functions are planned.

''This trip, like the previous two occasions she was here, is strictly private,'' said Pedro Borio, spokesman for the Brazilian Embassy.

Diana stayed at the ambassador's residence just after Christmas last year, and was spotted buying blue jeans at a local shop. Last summer, she visited the couple in Martha's Vineyard in Massachusetts.

This trip was to include a visit to the home of former Washington Post publisher Katharine Graham.

At the British Embassy, there was official silence. ''We don't discuss the details of private royal visits,'' said spokesman Peter Bean.

Britain has been abuzz since the first installment of ''Prince of Wales'' by Jonathan Dimbleby was published last Sunday. It said the prince never loved Diana and was forced to marry her by his domineering father.

Also, the Daily Mirror reported that the couple's attempt to negotiate a divorce was being delayed because Diana wants to keep the title, Her Royal Highness.