THE WORLD'S richest countries now funnel most of their development aid to the poor countries through the World Bank.But every year when Congress takes up the bill to appropriate the American share of this aid, there's an attempt to wreck this great common endeavor. This year, unfortunately, the wreckers' amendment passed the House.

It says that none of the American contribution can go to any of a short list of unpopular countries, headed by Vietnam. But all the money goes into one pot at the World Bank, the American money along with the money from the Germans and the British and the Kuwaitis and all the others. The World Bank's rules prohibit it from accepting money that carries discriminatory conditions. Otherwise, any donor country would be able to impose its own purposes and prejudices on the World Bank's whole operation.

In addition to Vietnam, the House amendment would prohibit the bank from aiding Laos, Cambodia, Angola and the Central African Republic. Why no help for the Central African Republic, where the average annual income is $250 and life expectancy is 27 years shorter than in the United States? Because the Central African Republic was ruled by the Emperor Bokassa, a man of whom the House disapproved. World Bank aid did nothing to support him while he was there, and the House vote contributed nothing to forcing him out. But he has departed since the House voted and, had it been the final vote in Congress, his unfortunate country would have remained cut off from any hope of further aid from the World Bank.

The Senate Appropriations Committee has reported the bank bill in decent and responsible form. When it comes to the Senate floor this week, someone will certainly attempt to impose the House amendment. Its purpose needs to be clearly stated. It is not intended merely to prevent American dollars from going to five small countries that Congress doesn't like, but rather to destroy American participation in the World Bank. That would destroy the bank itself.

The bank is an enterprise in which Americans can take deep pride. Under American leadership it has made large contributions to the conditions of life in the world's poorest regions. That work is steadily gaining momentum. It would be terrible now to let the wreckers win.