PRESUMABLY THE richest country in the world has a responsibility to help the development of the poorest countries. Most Americans support that principle, although perhaps not very vigorously. The appropriations bills that contain the aid money always take a terrible battering, and development aid never seems to be high on the list of national priorities.

Last week the secretary of the Treasury, James A. Baker, took the administration's request for the international development banks up to Congress for the first hearings. The chairman of the Senate subcommittee, Robert W. Kasten, observed that it would be very difficult to provide the full amount in a year in which nearly everything else in the budget was being cut. The chairman of the House subcommittee, David Obey, told the secretary that he was sympathetic to the request, but it will not be approved until there's a general agreement between the administration and Congress on the budget as a whole.

The United States provides foreign aid through two routes. Some of the aid goes directly from this country to the recipient. Some of it goes to international agencies like the World Bank, and this year the administration is asking Congress for $1.4 billion for them. Most of the money this year is earmarked not merely for poor countries, but for the poorest of the poor.

Just over half of the $1.4 billion is this year's payment on the American pledge to a subsidiary of the World Bank called IDA -- the International Development Association. It provides 50-year loans at very low interest to those countries that cannot afford the World Bank's usual terms. IDA was established at American initiative during the Eisenhower administration in order to induce the other industrial countries to share more of the cost of foreign aid. It still works that way. The American contribution of $750 million to IDA this year will be matched by $2.25 billion from the other members.

In addition to the money for IDA, this year's bill contains another $236 million for the African and Asian development banks and funds. Does this aid make any difference? At the time IDA was set up there was great concern over India, which seemed to be condemned to increasing starvation. But over the years India's food production has kept pace with population and its economy has strengthened steadily. By the 1990s India will very possibly be too prosperous to qualify for much of IDA's help. Now the focus is swinging toward sub-Saharan Africa, the only region of the world in which conditions have actually deteriorated over the past decade. As the bill begins to move slowly through Congress, it's important to remember who will suffer if it should fail.