Developing countries are entering a new, more difficult phase of their debt problem in which they must struggle to resume normal growth while paying off their loans, two-thirds of which come due in the next five years, the World Bank reported yesterday.

Because of the debt crisis of the last three years, "Dozens of countries have lost a decade or more of development," the bank said in its annual world development report.

Average per-capita real incomes in most of Africa are no higher than they were in 1970, and incomes in much of Latin America are back to the levels of about a decade ago, the bank said.

World Bank President A. W. Clausen, in a speech scheduled for delivery in Rome today, said that the policies adopted by the industrial and developing nations in the next five years "will determine whether developing countries make a smooth adjustment back to creditworthiness and steady growth, or whether debt-servicing difficulties will once again disrupt their progress."

"In the next five years, about 60 percent of the debt of the developing countries will need to be rolled over or amortized," Clausen said. "At the same time, the international community must respond to the needs of the poorest countries for sustained and increased flows of capital."

Whether developing countries will be able to pay off their debts and increase growth will depend on economic policies of industrial countries, particularly the United States, the report said. The loose fiscal and tight monetary policies of the United States have led to high interest rates that add to the debt-servicing costs of developing countries.

"The prospects for the next 10 years do not exclude the possibility of further debt-servicing difficulty for many developing countries," the bank said. "The world economy does not need to slump as it did in 1981-1982 for debt problems to recur."

If the economies of industrial countries grow at 2.7 percent a year for the next five years, combined with high real-interest rates and increased protectionism, "several groups of developing countries could find themselves with heavier debt-servicing burdens at the end of this decade than they had at the beginning."

The International Monetary Fund recently predicted that the major industrial economies will grow at an average rate of 3 percent a year.

The World Bank proposed two scenarios for industrial country growth in determining how well developing countries will be able to increase exports to service their debts and foster internal growth.

The low-growth case projects industrial country gross domestic product (GDP) to grow at only 2.7 percent annually, and the GDP of all developing countries to grow at an annual average of 4.1 percent. Real-interest rates would remain virtually unchanged and export growth would increase 3.5 percent.

In the high-growth scenario, GDP of the industrial nations would rise at an annual average rate of 3.5 percent, and the GDP of all developing countries at 5.5 percent, the World Bank said. Inflation in industrial countries would be below 8 percent and real interest rates would fall to 2.5 percent from the 6.8 percent average between 1980 and 1985.

The bank said that the more upbeat growth scenario is not impossible to achieve.

The World Bank report is concerned particularly with the developing country debt that will come due between now and 1990. Between 1970 and 1984, the outstanding medium- and long-term debt of Third World countries grew almost tenfold, the bank said.

Lending by banks grew most strikingly with their share of total new capital flows to developing countries, increasing from 15 percent in 1970 to 36 percent in 1983, the World Bank said.

The number of debt reschedulings for World Bank members increased from an average of less than four each year in 1975-80 to 13 in 1981 and 31 in 1983, the bank said. About that same number of debt negotiations took place last year, but agreement was reached only on 21.

The bank urged that multi-year debt reschedulings continue and be extended to some middle-income countries and to many low-income African countries "in which debt-servicing difficulties and development problems are intertwined."