Japan announced Saturday it will boost its aid to Third World debtor nations by $50 billion over five years and provide immediate debt relief to 17 of the poorest African and Asian debtor nations.

At a briefing before the start of the Toronto Economic Summit, Michihiko Kunihiro, chief cabinet counselor for external affairs, said the new aid program will be more than double the volume of Japanese aid to debtor nations over the past five years.Japan in recent years has come under increasing criticism for failing to assume a greater role in easing the $1.2-trillion Third World debt. U.S. officials reportedly want Japan - which enjoys a $96.5-billion trade surplus - to provide greater aid to strategically located Third World nations. Such action is seen as an alternative to boosting military spending.

About $1 billion in relief will come from a program of stretching out debt payments on $5.5 billion in loans provided to 17 of the poorest nations since 1978, Kunihiro said.

"These are the countries that are really suffering," he said. "Unless the burden is lifted they have no hope of repaying the debt."

In addition, Kunihiro said Japan's contributions to Third World debtors will increase in proportion with growth in Japan's economy.

Earlier, Canadian officials said Japanese Prime Minister Noboru Takeshita, responding to an invitation from Prime Minister Brian Mulroney, will lead a discussion about newly industrialized countries of Asia at the economic summit.

Officials told reporters the invitation was issued during a bilateral meeting earlier in the day between the two statesmen.

The Japanese leader also urged Mulroney to raise the problem of newly industrialized countries in Asia, such as Singapore, South Korea and Taiwan, whose trade surpluses threaten a global move toward more liberalized trade.