When it comes to the Mayor with the Mouth, there may be little news lately, but there's always something to talk about.

The latest tongue-wagging episode in the midst of a lethargic reelection campaign is a bundle of leaked tidbits from a forthcoming book entitled, "I, Koch -- A Decidedly Unauthorized Biography of the Mayor of New York City, Edward I. Koch."

In the book, written by former city hall reporters Dan Collins, Arthur Browne and Michael Goodwin, Koch is quoted as having called Rep. Ronald V. Dellums (D-Calif.) "a Zulu warrior" and "a Watusi from Berkeley."

Koch acknowledges having made the remarks 10 years ago when he and Dellums, an advocate of Palestinian rights, were at odds over Middle East policy, but he said they were not meant to be insulting.

"It happens you can't compliment someone more than you would if you refer to them as a Zulu warrior," he told city hall reporters. "Zulus were the major tribe of extraordinary bravery in Africa that defeated in several battles the Boers and English," he added, calling himself "an aficionado of the subject."

As for Watusis, Koch said, they were "kings in their own lands -- the two countries of Burundi and Rwanda. And they still run Rwanda." The Watusis, he said, are "very tall and handsome . . . . If you've ever seen Ron Dellums, you will know what I meant. He is very imposing."

Nonetheless, Koch, who has been criticized by blacks in recent years for racial insensitivity, made a conciliatory telephone call to the California congressman Tuesday. And on Wednesday, the mayor, in Washington for a congressional hearing, ran into Dellums in the Capitol.

"We shook hands and kind of embraced, really," Koch said today. "I put my hand on his shoulder and told him, 'I really want to thank you for the response you gave.' And he said, 'I know what they're trying to do. They're trying to come between us and it won't happen.' "

Dellums has declined to comment publicly. A Dellums spokesman has said Dellums "accepts Koch's explanation."

Rep. Charles B. Rangel (D-N.Y.), who represents Harlem, said, "The whole world knows what the mayor intended," and he expressed "surprise at the benevolence of our colleague at Berkeley." Asked what exactly Koch intended, Rangel said, "I would not touch it with a 10-foot pole."

Koch's two opponents in the Sept. 11 primary are not amused. City Council President Carol Bellamy called his remarks "outrageous, bigoted and an affront to all New Yorkers." Assemblyman Herman D. Farrell, a black, said the "derogatory" remarks show "a pattern that continues today and polarizes the city. The voters, both black and white, know they can't continue to have a mayor who is so divisive."

Koch has denied a third quote attributed to him in the book by an unnamed journalist with a major New York daily. The journalist reported that shortly after Koch's election as mayor in 1977, during a social evening, he repeatedly referred to blacks by the derogatory Yiddish term "schvarzes."

The book is scheduled to be published next month, but the Dellums quotes and other selections were published Tuesday in the New York Post under the headlines, "Koch's Secret Teen Romance . . . and other believe-it-or-not-Edlines."

The "romance" in question was a high school date in which Koch, a lifelong bachelor, was reported to have been forward with a young woman.

Koch, who is considered to be the election front-runner, has raised a $5 million campaign chest, largely from real estate and financial interests. Bellamy has raised about $615,000 and Farrell, a victim of infighting among the city's black politicians, has raised $111,000.