The major industrial powers must grant the poorest African countries more debt relief if that continent is to enhance its economic prospects, International Monetary Fund Managing Director Michel Camdessus said Tuesday.

But World Bank President Barber Conable said that although the World Bank and the IMF can aid Africa through lending programs, those countries must also take responsibility for their economic recovery.Sub-Saharan Africa uses about half its export earnings to service around $135 billion of debt. The continent's economically troubled nations are also facing increasing competition for financial aid and investment from Eastern Europe and Latin America.

"Not surprisingly, private investment has all but dried up and net transfers to the region are negative," Mr. Conable said.

Both officials underscored the need for continued assistance to Africa's poorest countries in speeches before the Bretton Woods Committee.

''Creditor governments will need to take a more generous approach to debt relief, otherwise the heavy overhang of official debt may undermine the chances of success," Mr. Camdessus told the meeting of central bank economists and other government officials who monitor global economic initiatives. Mr. Camdessus noted that some debt of those nations has already been forgiven in the wake of the economic summit in Toronto, but "the problem of middle-income countries with a heavy burden of official debt should be addressed meaningfully."

He said that the IMF's ability to help Africa largely depends on how much fund members are willing to increase their contributions to the IMF.

The United States, which has the major voice in the IMF, appears to be ready to back more than a 50 percent boost, though less than the doubling of the $120 billion in the quota previously sought by Mr. Camdessus. He told reporters that he expects the quota to increase in the lower part of the 50 percent to 70 percent range. The precise terms are expected to be resolved in an upcoming meeting of the IMF's policy-making committee.