At one point in the "Dance in America" segment devoted to his work (at 9 tonight on Channel 26), choreographer Merce Cunningham says about the program, "there is even comic relief - although you may place this at a different moment than I do."

It's typical Cunningham, and it gives away in a flash his desire not to encumber his audience with preconceptions, his sense of mischief, his love of enigma. This is one of several particularly revealing instants in a program that, on the whole, bites off more than it can comfortable chew.

Cunningham has had some previous television exposure, but nothing before on the scale of this 60-minute color program to be shown nationally on public TV. Those who will be encountering his work for the first time are given a broad sampling, stretching from "Septet" and "Minutiae" from the early '50s, to Video Triangle," newly created specifically for "Dance in America." There are musical adjuncts by John Cage and David Tudor, and sets and costumes by Rauschenberg, Warhol, Jasper Johns and others.

The picture that emerges, however, is not only partial but in some respects misleading. Cunningham's work depends on a sense of spatial scale and volume the flat screen contradicts. Neither Cunningham himself, in his mid-50s, nor the dancers of his present entourage fairly represent the troupe at its past level of performing excellence. Most disappointing of all is the unadventurous use of the video medium, the more surprising in view of Cunningham's own maverick spirit.