In "U.N. Deadbeat" {editorial, Oct. 7}, The Post refers to the continuing failure of the United States to pay its assessed contribution to the United Nations. It does not mention, however, that the United States is also in default in the World Health Organization and several other specialized agencies of the United Nations.

The editorial mentions the political and managerial reform that has taken place in the United Nations. The World Health Organization has also reformed its budget decision-making process along the lines required by Congress.

To date, the United States owes WHO more than $100 million.

By voting "yes" on the WHO biennial budget for 1986-1987, the U.S. government agreed to pay WHO $125.6 million to help finance activities in 1986 and 1987. One-half this amount was due on Jan. 1, 1986, and one-half was due on Jan. 1, 1987. The United States still owes WHO $37.4 million for 1986. A check is in the mail for $17 million, the final payment on the 1986 contribution, but this will leave arrears of more than $20 million.

There has been no payment on the $62.8 million due for 1987. The appropriations legislation now pending falls far short of providing sufficient funds to pay the full U.S. obligation to WHO, to the other specialized agencies and to the Pan American Health Organization.

The failure of the United States to pay its assessed contribution has forced WHO to cut substantially its 1986-1987 program activities and to project additional massive cuts in future activities. WHO has had to reduce its staff, close offices and cancel programs. The across-the-board cutbacks are spread over a wide variety of activities, ranging from nutrition and sanitation to malaria control.

The shortfall in the U.S. contribution has reduced WHO's capacity to support its ongoing program activities, including its special program on AIDS. AIDS program activities are funded from voluntary contributions, but the AIDS program depends on the infrastructure of WHO for support, to field experts and to manage resources, for example. The AIDS program is putting a tremendous strain on the organization, which is getting weaker each day the U.S. contribution continues to be withheld.

The United States is the only industrialized country in arrears for 1986. The Soviet Union, China, Japan, Canada, Australia and all the European allies have paid their full 1986 contribution to WHO. For 1987, the European allies have paid their contribution in full, as have China and many Eastern European countries. The Soviet Union has paid two-thirds of its 1987 contribution.

The United States was one of the founders of WHO and has always played an important leadership role in the organization. But the failure of the United States to meet its financial obligations is placing that role in jeopardy and is being widely perceived as a lack of political commitment by the United States to the fundamental principle of better health for all. MARJORY DAM External Relations Officer Office of the Director-General World Health Organization Washington