A proposal that the United Nations celebrate the 500th anniversary of Christopher Columbus' discovery of the New World fell off the edge of the Earth yesterday when the Africans decided the celebration would amount to honoring a colonialist.

Their opposition was aroused after Iceland's Ambassador Hodur Helgason insisted in a General Assembly debate that "America was discovered by Leif Ericsson, an Icelander of Norwegian descent in the year 1000."

Then Helgason mentioned tongue-in-cheek that the resolution -- which would have launched U.N. planning for "appropriate observances" in 1992 -- would be the first in U.N. history "which commemorates colonization."

The sponsors of the draft, among them Spain and 29 New World nations including Cuba and the United States, suddenly found their proposal foundering.

The 50 African states, sensitive on the issue of colonialism, caucused and decided to vote against the resolution en masse. Yesterday, U.N. officials announced that the vote, scheduled for Monday, had been put off indefinitely -- most likely until at least next year.

Besides the Africans, Ireland also took a dim view of the proposal to honor Columbus. Irish Ambassador Noel Dorr suggested that an Irish monk, St. Brendan the Navigator, may have discovered America as early as the 7th century, and he criticized the sponsors for wasting U.N. time and money on the issue.

Jaime de Pinies of Spain retorted that the only thing that the Irish have contributed to the American continent "is the well-trained police force in New York City."