TOKYO, OCT. 30 -- African National Congress leader Nelson Mandela accused the Japanese government today of not doing enough to support blacks struggling for equality in South Africa.

Mandela, sounding like Americans who have charged that Japan has failed to provide sufficient support in the Persian Gulf crisis, told a packed news conference here that "the contribution made by the Japanese government is absolutely insignificant."

"If you compare it to what has been done by very poor countries in Africa, and the countries we just visited in Asia, and the other countries in the West . . . again, the contribution of the Japanese government has been very insignificant," Mandela said.

The 72-year-old Mandela, stopping here for six days during a tour of Asia, has received a virtual hero's welcome from the Japanese people, with long lines waiting at every stop and saturation media coverage. But in his appeals for aid from the Japanese government, Mandela has evidently struck out.

On Monday, Mandela met with Kaifu and asked for a grant of $25 million to the African National Congress. Kaifu responded that "there is no precedent" for the Japanese government to provide "direct assistance" to political groups. As a result, Kaifu said, "it will be difficult" to grant Mandela's request, but he said Japan might consider funding aid to the ANC through a group such as the United Nations.

Given the lack of clarity inherent in Japanese language and culture, where a certain ambiguity is considered good form, it was not absolutely clear that Kaifu's answer constituted a rejection of Mandela's request. Of the five big national newspapers here, three reported Kaifu's answer as a rejection, one said it sounded positive, and one said the response was unclear.

But Mandela clearly took Kaifu's reply to mean "No." At his press conference today, he contrasted Japan's rejection with positive replies he had received from other Asian countries during his current trip.

One area where Japan's government was willing to break precedent for Mandela was in the Diet chamber, where the visiting South African addressed both houses of parliament, an honor normally reserved only for heads of state.