On the day Geraldine Ferraro arrived in Japan last month, an ad in the Tokyo newspaper Sankei Shimbun showed her sitting relaxed before an open book, a string of pearls around her neck.

"Do you notice on her chest, her ears, she always wears pearls?" asks the main ad copy in Japanese characters. "The politician who loves pearls more than any other jewelry . . . will again restart her career as a candidate for next year's Senate race at the beginning of this fall . . . Today she steps on Japanese soil as a warmup.

"Japan, country of pearls," comes the finale. "Let us welcome from the bottom of our hearts, someone who loves pearls." In bold print in the top right corner of the ad is the logo for Tasaki Pearls.

No, the former Democratic vice presidential candidate has not gone endorsement-crazy after her Pepsi ads, for which she received a reported $500,000. In fact, insists her office, she knew nothing about the ad for pearls until it appeared July 27.

"She was very unhappy about the ad ," said Ferraro spokeswoman and former campaign fundraiser Addie Gugtag yesterday.

Ferraro arrived in Japan last month, Gugtag said, to make the keynote speech on July 30 for Tasaki Shinju Forum 1, a Japanese conference on women's issues following up the U.N. Women's Decade Conference in Nairobi.

The contract for her appearance stipulated a fee for the speech, Gugtag said, but there was no mention of commercial endorsements. Gugtag would not discuss the size of the fee.

Learning of the ad upon arrival, Gugtag said, Ferraro asked for a translation. The promoters of the conference, a Japanese agency called Dentsu Eye Inc., assured her she was advertising only the forum, Gugtag said, but Ferraro remained skeptical.

"They did not give clear enough information, so she asked people at the American embassy," the spokeswoman continued. "They said, in fact, it was advertising pearls."

When Ferraro confronted representatives of Dentsu Eye -- an affiliate of Dentsu Inc., Japan's largest public relations/advertising firm -- about the ad, "they said it was a staff error and it won't happen again," Gugtag said.

Ferraro does not plan to sue Tasaki or Dentsu Inc., Gugtag said, but she told a luncheon group of Tokyo-based foreign journalists to "alert" her if they saw repetitions of the ad. " 'There's nothing I can do about it,' " Gugtag reported Ferraro as saying. " 'If anyone sees it again, please alert me to it . . . I'll have to take action.'

"I think Tasaki may have been one of the sponsors behind the forum," said Gugtag. "Or possibly a client of Dentsu Eye."

Spokesmen for either Tasaki or Dentsu Inc. in Japan could not be reached for comment.

" Dentsu Eye Inc. had met with us about late May or early June," said Gugtag. "And they took a photo for advertising the conference. We were supposed to get to see the ad and they would translate it for us. They had not done that."

As for an accompanying childhood photograph of Ferraro in the ad, she said, "We don't know how they got that."

Ferraro and her family had planned a three-week visit of the Orient, Gugtag said, on the occasion of the 25th wedding anniversary of Ferraro and her husband. The trip included a stop in China and "official" meetings with Chinese and Japanese officials, including Japanese Prime Minister Yasuhiro Nakasone. The forum speech was the only occasion for which Ferraro was paid, Gugtag said.

Dentsu Eye Inc., which made initial contact with Ferraro shortly after the 1984 election, "kept pursuing," so since Ferraro and her husband would be in the Orient, Gugtag said, "they said 'Okay.' "

Ferraro is putting the finishing touches on her book, "Ferraro: My Story," and is still undecided about running for Sen. Alfonse D'Amato's 1986 seat, Gugtag said. Ferraro will not endorse any more products, Gugtag added.

"The only reason she did the Pepsi ad was to show . . . she was not putting down housewives" by running for president, Gugtag said. "She feels strongly mothering/running a house is a very important job."

Ferraro, Gugtag said, will "always do public speaking as long as anyone is interested in hearing her."