FOR THE second time in two years, American Ballet Theatre has chosen to unveil a major new production here in Washington. The present one, like the "Nutcracker" of 1976, is the work of the company's celebrated dancer, Mikhail Baryshnikov, who now offers us an ambitious new version of the Russian ballet classic, "Don Quixote."

The new opus will have its world premiere Thursday evening in the Kennedy Center Opera House, with settings and costumes by Santo Loquasto and lighting by Jennifer Tipton. Heading the cast will be Baryshnikov himself as Don Basil and Gelsey Kirkland as Kitri; the key non-dancing roles of Quixote and Sancho Panza will be taken by Alexander Minz and Enrique Martinez. In the pit will be the distinguished British conductor John Lanchberry, reportedly on the verge of being named musical director of ABT.

Baryshnikov is calling the ballet "Don Quixote or Kitri's Wedding," intending the second half of the title to indicate the lighthearted nature of the work. "It's romantic comedy, nothing else," he says, and he once thought of subtitling it "a romantic vaudeville."

For most balletgoers, mention of "Don Q" conjures up images of the flamboyant pas de deux by that name which is one of the standard showpieces of classical ballet - Baryshnikov dances it with Leslie Browne in the movie, "The Turning Point."

This virtuosic duet is all that has remained in western repertory of a full-length ballet originally choreographed by Marius Petipa in Russia in 1869.The Petipa "Don Quixote," as amended by Alexander Gorsky and others, has been seen in this country during visits of the Bolshoi Ballet.

The ballet public is familiar with two other relatively recent full-length versions - the Rudolf Nureyev production, made into a motion picture in 1973, and the quite constrasting, serious and sumptuous George Balanchine version created in 1965. The Baryshnikov ballet, however, though it is closely modeled on the Petipa-Gorsky staging, is in a different vein altogether from these other modern rescensions.

One thing they all have in common is the Cervantes novel. But the Balanchine version aside, these ballets have shunted Quixote himself into the position of catalyst for the action, rather than its heroic center, and taken as a plot a little ancillary tale in the book about a village girl, Quiteria (who becomes Kitri in the ballet) and her lover, the barber Don Basil. Thus Baryshnikov's has attempted to weave the role of Quixote and the Basil-Kitri story into a tighter unity than in previous versions, and to this end he begins the ballet with one of his innovative scenes, a brief Prologue. Don Quixote and Sancho Panza are seen entering from opposite sides, and then, against the background of a windmill, Quixote sees a vision of Dulcinea (also a non-dancing role), his image of ideal womanhood.

Then Kitri, Basil and all the subsidiary characters are introduced, and in masks, almost in commedia dell' arte fashion, they enact in miniature the story that is to follow - Kitri's love for Basil, her father's attempts to pair her off with the rich Gamache, and the [WORD ILLEGIBLE] the lovers employ to achieve their happy union. Amor (Cupid), who is one of the characters, shoots all with his amorous arrow, whereupon they disappear, and Quixote sets out in quest of his vision.

In the succeeding first act, the basic predicament is set forth in detail, against the colorful hubbub of the town marketplace - the attachment of Kitri and Basil, the objections of the father and Gamache. Basil adn Kitri flee to a Gypsy camp, the side of the opening scene of Act II. It is here that the paths of Quixote and Kitri intersect, for seeing her in front of the windmills, he confuses her with Dulcinea and attacks them to protect her. There follows a dream sequence in which the women in Quixote's life - Dulcinea, Kitri, a beautiful street dancer - all seem to merge.

Things come to a head in a tavern scene, wherein Gamache and Kitri's father arrive in pursuit of the lovers. To skirt defeat, Basil feigns suicide, and at the urgings of Kitri, Don Quixote persuades the father to permit Kitri to wed the "dead" Basil as a gesture. The ceremony takes place, whereupon Basil instantly recovers, and Gamache and the father reconcile themselves to the turn of events. The last act is a wedding celebration - like so much of the rest of the ballet, an apt excuse for dancing galore. At the very end, Quixote has a final vision of Dulcinea and sets out in search of her once more, thus bringing the action full circle.

Petipa's Spain, which is the setting for all this, is clearly a stage figment, but it nevertheless had some basis in biographical fact. The prolific choreographer spent some early years in Spain and, according to his memoirs, even had some romantic adventures of his own there, including a duel over a lady's honor.

He also wrote, very proudly, that "I became acquainted with Spain dances at the source, on the spot." In "Don Quixote" he found an extremely useful outlet for this acquired knowledge, and one very much to the taste of the Moscow audience for which he created it. It was a ballet, moreover, that permitted in its Spanish ambiance not only the natural introduction of sequidillas, fandangos and other "character" dances, but also all manner of "exotic" peripheral characters.

Baryshnikov has tried to retain the same florid atmosphers and detail, so that his ballet also has its complement both of Spanish dance rhythms (to the same Leon Minkus score Petipa commissioned) and matadors, toreadors, street dancers, flower girls and Gypsies. At the same time, he felt the tone warranted modification for contemporary sensibilities.

"The ballet is basically the Petipa-Gorsky version I knew so well from my upbringing with Kirov Ballet," he says, "but as seen from my own, quite personal angle of vision. One cannot take the story, the ballet, with the same seriousness as they did in the 19th century, so my point of view is more ironical. It would have been easier to just recreate the old version as I learned it, but for an American audience, this would have seemed like a museum piece, so I tried, particularly in the prologue, the new finale I made and some additional touches in between, to present my viewpoint - to lighten things up. This may be risky - some people will say, if you are going to do Petipa at all, do it the way it was, and they may be right. But I felt I had to have the guts to put forward my own idea."

Baryshnikov has also abridged the original. "This was a very long ballet," he observes, "five acts, each an hour - still today when the Kirov performs it, it goes from 7 p.m. to midnight. I cut back the mime and speeded it up, and cut some dances too - for example, a celebrated Petipa dance in Act I involving Sancho Panza. To me, it seemed to step the action, it had no relation to the Kitri story, and neither the music nor the choreography was very distinguished.

"What I kept was what I felt to be the finest of the choreography, and the mime essential to the telling of the story." He also added some new dancing for his own dramatic purposes and to suit the company, including, besides the already mentioned finale, a Gypsy pas de deux, solo variations for a matador, for Basil and Kitri, and various transitional sequences.

His slant on the major characters also accords with his "romantic vaudeville" conception. "I only wanted to concentrate on one aspect of Don Quixote - his romantic view of woman. There seemed no sense in trying to present other, 'deeper,' dimensions - there are no giants here, no extravagant escapades. The same with Sancho Panza - I present just one side of him, the one realistic fellow in the ballet, who cares about a glass of wine and a tasty meal. Dulcinea I included simply as a motivation for Quixote. Gamache, however, I made a large role than in the past and also more sympathetic." He sees Basil as a shrewd wit, "a sort of balletic Figaro," as he puts it, with the resourceful wench Kitri as his Susanna.

Baryshnikov also regards this "Don Quixote" as a taxing and potentially fruitful challenge in theatrical savvy for the company. "Everyone will have some freedom within the action to help create their parts," he says, "and it will work if the dancers believe in what they're doing. With 40 or 50 people onstage, I cannot possibly direct every step for each person, nor can I teach them in the time at hand how to react to their partners, how to wave a fan, how to feel free in their costumes, how to make a greeting, how to talk, to walk, to take a drink. So it will be very much up to them."

The whole effort to mount the ballet, which began last September, has taken place under the most contracted and trying conditions, with rehearsals caught on the fly in between the exhausting preparations and performances of an extended cross-country tour. At times, even Baryshnikov's ordinarily sunny nature seemed strained to the cracking point.

If you ask him now about future choreographic projects, he will smile that incredibly disarming smile of his, shake his head and exclaim vigorously, "Never, never, never, never and never - this is the end." That is, of course, precisely what he said after "Nutcracker."