FOR THE first time since the company has been visiting here, the New York City Ballet will offer the Washington public the premiere of a ballet -- Peter Martins' "Lille Suite" -- during its two-week Kennedy Center engagement, which starts Wednesday evening. True, it won't be a world premiere (that took place in Copenhagen this past August), but it will be an American premiere, and thereby a sign of recognition of the burgeoning importance of the troupe's annual visits to this city.

In addition, among the total of 16 ballets the company will stage in the next fortnight there'll be five Kennedy Center premieres of ballets by George Balanchine, Jerome Robbins and Martins.

The perennial vicisstudes of dance have induced some changes in what was originally planned for the Kennedy Center visit. Ballerina Merill Ashley, perhaps the most electrifying virtuoso among the company's present female principals, won't be dancing in Washington this time: She's nursing a hip injury from last summer that's been acting up. Kay Mazzo, another principal, will be away on maternity leave.

The absence of Ashley has necessitated the postponement of the Washington premiere of Balanchine's "Ballade," a much-praised ballet to the music of Gabriel Faure that marked the Choreographer's first major creative effort since his heart surgery of 1979. And without Mazzo, Balanchine's "Duo Concertant," one of the treasures of the company's 1972 Stravinsky Festival, had to be replaced.

However, City Ballet has compensated for these deprivations by giving us the U.S. premiere of Martins' "Lille Suite," instead of saving it, as originally intended, for the company's regular New York season starting in November.

"Lille [Danish for little] Suite" is an abstract ballet for a principle couple and 12 women, set to music by the most celebrated of Danish composers, Carl Nielsen (1865-1931). The "Little Suite in A Minor for String Quartet, Op.1," written in 1888, thus becomes the first Nielsen work to enter the NYC Ballet's unusually extensive musical repertoire. Martins choreographed the ballet especially for the company's visit to Copenhagen, his birthplace, and it received its premiere there at the Tivoli Concert Hall. The first of four Kennedy Center performances will take place on Friday evening.

Still remaining in the Kennedy Center lineup are Balanchine's two other most recent works, "Walpurgisnacht Ballet" and "Robert Schumann's Davidsbudnlertanze,'" both of which will receive their Washington premieres during the second week of the troupe's visit. "Walpurgisnacht Ballet" is an elaborate divertissement orgiginally created for the 1975 Paris Opera producition of Gounod's opera "Faust, which was first mounted by City Ballet early this year. "Robert Schumann's 'Davidsbundlertanze,'" widely regarded as Balanchine's most ambitious effort in some years, sets four couples dancing to a collection of piano pieces by the famous romantic composer of the title.

Also new to Kennedy Center will be that model of neo-classical purity, Balanchine's "Apollo," in the master's controversial revised version of 1979; Jerome Robbins' "Suite of Dances (from Dybbuk Variations)," an excerpting of the men's dances from Robbins' 1974 collaboration with composer Leonard Bernstein; and Peter Martins' "Eight Easy Pieces," a women's trio set to a two-piano score by Stravinsky.

The remainder of the repertory includes three performances of Balanchine's evening-length favorite, "Jewels," as well as his compact version of "Swan Lake," and also "Firebird, "Cortege Hongrois," "Concerto Barocco," "Brahms-Schoenberg Quartet," "Western Symphony," "Divertimento from 'Le Baiser de la Fee,'" and "Symphony in C." Robbins' "afternoon of a Faun" completes the list.

A special feature of the run will be an "all-Stravinsky" program to be presented once only Saturday evening, consisting of "Divertimento from "Le Baiser de la Fee,'" "Eight Easy Pieces," "Apollo" and "Firebird."

There'll be four newcomers to the rank of principal dancer for this visit: Ib Anderson, formerly of the Royal Danish Ballet; and Kyra Nichols, Heather Watts, Bart Cook and Daniel Duell, all promoted from soloist rank this past spring.

The City Ballet appearances also mark the launching of this year's Kenndy Center ballet series, which later in the season will include American Ballet Theatre, the Dance Theatre of Harlem, the Eliot Feld Ballet, the Martha Graham Dance Company, and next summer, England's Royal Ballet.