NAIROBI, KENYA, JUNE 6 -- In the aftermath of the major African famine of 1984-85, rain returned to the continent, hungry children stopped dying and two dozen poor countries began to admit the obvious.

Their leaders conceded that bad government was, in large measure, responsible for Africa's accelerating poverty. With that admission came a wave of economic reform.

Government deficits declined. Parasitic bureaucracies were dismantled. Farm prices increased, and farmers, always eager to make a living, produced more food.

Reform grinds on, as it must for years. But now there is a growing sense of unease among African governments and western financial authorities that Africa's poorest countries are again on the verge of collapse. While not as easily dramatized as the famine, these authorities say the looming crisis may be more serious and its effects more long-lasting.

The emergency is the result of a convergence of unpayable international debts with a collapse in world prices for the farm exports that keep African economies alive.

African specialists at the United Nations, the World Bank, the U.S. State Department, on Capitol Hill and in Western Europe agree that the crisis threatens to bankrupt and perhaps topple several African governments. If that were to happen, these specialists say Africa's best chance for economic self-sufficiency may be lost.

This sense of urgency has, for the first time, put African debt on the agenda at the economic summit of seven industrialized countries starting Monday in Venice. The debt issue is forcing western countries to consider a series of unprecedented maneuvers to postpone interest payments on African debts for 15 to 20 years, convert outstanding loans to gifts and sharply increase lending at low rates of interest.

"We are dealing with countries that have a stock of debt so high and export prospects so low that there is no way they can get out of debt with any kind of conventional borrowing," said Xavier de la Renaudiere, director of the World Bank's special fund for Africa.

According to the U.N.'s Economic Commission for Africa, the combination of falling commodity prices and rising debt payments bled Africa of about $30 billion in 1985-86.

"Africa, poor as it is, continues to be a net exporter of resources, paying more in debt service than the combined total of what it receives in foreign aid and earns from commodity exports," Adebayo Adedeji, the commission's executive director, said here last week.

The World Bank estimates that commodity prices are one-quarter to one-third what they were in the 1970s, when African leaders borrowed heavily to finance bloated governments.

"You cannot make bricks without straw. You cannot expect African countries to go through structural adjustment without resources to finance it," said Adedeji. "If the rest of the world cannot help Africa stand on its feet, then it will have to support a permanent emergency case."

Sub-Saharan Africa's total foreign debt is about $100 billion, a relatively modest figure by Latin American standards. Brazil alone owes more than $110 billion and Mexico more than $90 billion. But most African economies are minuscule. The entire purchasing power of a relatively prosperous country like Kenya is comparable to that of one big American city.

The cost of servicing Africa's debt is about $12 billion -- enough to eat up half the region's total export earnings, according to a study by the Overseas Development Council, a Washington think tank. Economists agree that such a high debt service bill makes it all but impossible for governments to make new investments for growth or even to import the fuel, fertilizer and spare parts needed to maintain current export levels.

"The way the region's debt problems have been allowed to progressively worsen borders on scandal," the Overseas Development Council study says. "The international community now faces the choice between urgently adjusting debt service schedules . . . or dooming the prospects of successful economic recovery for many African countries."

Even prosperous African countries are starting to fall by the wayside. Ivory Coast, one of the continent's most conspicuous economic successes and the world's third largest coffee producer, stunned financiers last week by announcing it would not pay the $1.18 billion due this year on its $8 billion debt.

A five-year low in coffee prices was cited by the country's finance minister as the reason why it could not, for the first time in 26 years, pay its bills.

More typical, however, of the severe political and social strain imposed by the combination of low commodity prices, high debt payments and painful economic reform is the case of Zambia.

Last year the World Bank and western donors proudly pointed to that southern African country as an example of how sound free-market principles could help pull a nation up by its bootstraps. Food subsidies were cut. The currency was devalued. Civil servants were fired. Farm production improved slightly.

The World Bank News said "observers are guardedly optimistic about the country's prospects for longer-term growth."

But in December it became clear that the average Zambian -- who since 1974 has lost two-thirds of his annual income due to a price collapse in copper, the country's main export -- was not nearly as optimistic as the World Bank News.

When President Kenneth Kaunda doubled the price of cornmeal, the staple food, Zambians rioted. Fifteen people were killed. The violence stopped only after Kaunda rescinded the price increase.

Last month, with debt, inflation, unemployment and urban discontent growing, Kaunda dumped Zambia's structural adjustment package worked out with the International Monetary Fund and the World Bank. Reform had done little, he said, to halt the fall of per capita income from $630 in 1981 to $200 this year. Kaunda blamed devaluation for revving up inflation from 21 to 61 percent.

"I am fully aware that this move will not be welcomed by all our creditors," said Kaunda, in his speech announcing that Zambia would pay only 10 percent of its export earnings for old debts.

"This is the only way this nation can survive," Kaunda said. "Which is a better partner for you in the long run, a nation which devotes all of its resources to paying the debt and, therefore, grinds to an economic and political halt, or a stable nation capable of sustaining the repayment of its entire debt?"

Zambia's fall from free-market grace has rung alarm bells in Europe and the United States. Officials of the U.S. Agency for International Development told congressional staff members last week in Washington that their agency and the World Bank had "underfunded" Zambia's reform program by $300 million.

More money would have smoothed Zambia's adjustment and helped head off political problems, the AID officials said.

Rushing to avert another Zambia, the World Bank (which plays no formal role in the Venice economic summit) has helped draft a debt-relief plan that will be presented at the meeting.

The plan calls for $20 billion to $25 billion in debt relief for 12 debt-distressed African countries, according to the World Bank's Renaudiere. The 12 are Gambia, Madagascar, Mali, Mauritania, Niger, Senegal, Sierra Leone, Somalia, Tanzania, Togo, Zaire and Zambia.

He said the goal would be to reduce quickly the countries' debt burden to about 20 to 25 percent of their export earnings.

Unlike Latin America, where most debt is held by private banks, about 80 percent of the total foreign debt of poor African countries is owed to western governments and multilateral agencies like the World Bank and the IMF.

"In terms of real cost for creditor countries {African debt relief} is very modest as compared to the kind of staggering figures one hears from other regions of the world," Renaudiere said.

He said that World Bank calculations show the cost of postponing interest payments on $25 billion worth of debt owed by the 12 debt-distressed countries would be about $700 million a year. He added that extra "concessional assistance," low-interest loans or grants, also would be needed to allow these countries to import the fuel, machinery and spare parts needed for growth.

According to the World Bank and several other sources, there is widespread support for the African debt plan from Italy, France, Canada and Britain. The major opponent is expected to be the United States.

The Reagan administration, according to U.N. sources, has resisted joint action among industrialized countries on Africa's debt. It is said to prefer individual negotiations between creditor and debtor nations.

Although the U.S. government was responsible for about one-third of worldwide famine assistance to Africa in 1984 and 1985, Washington's bilateral assistance to sub-Saharan Africa has fallen by $181 million between 1984 and 1987.

According to figures prepared by Rep. Howard Wolpe (D-Wis.), chairman of the House Africa subcommittee, the share of total U.S. foreign aid going to sub-Saharan Africa has declined from nearly 14 percent to less than 10 percent in the past three years.

Wolpe, who has proposed additional spending for Africa, says the decline is particularly ill-timed because "no region has experienced the steep economic decline that Africa has in the past few years."

One year ago, the U.S. government took the lead in advocating free-market reform during a special U.N. session on Africa's economic problems. U.N. officials claim that the United States now has an obligation to provide additional support to those countries that took its advice, but continue to struggle economically.