Sir Kenneth MacMillan's "Romeo and Juliet," to Prokofiev's score, provides as many opportunities for character development as dancing, and in its initial performance by American Ballet Theatre Friday night at Kennedy Center's Opera House, the company offered as fine an example of ensemble acting as it has displayed this season. Even secondary and tertiary roles were cast strongly, and the production itself, with its striking sets and costumes by Nicholas Georgiadis, offered a striking portrait of Renaissance Italy as a backdrop for the tragic story.

The passion in "Romeo and Juliet," of course, is provided by the lovers, and Alessandra Ferri and Kevin McKenzie both delivered passionate performances, beautifully danced. Yet, although they were well matched, the dancers must tell the story anew rather than merely react to cues, and Ferri and McKenzie were so intent on dancing "passion" that they forgot to fall in love.

Ferri was a very knowing Juliet. She seemed so ready for love and so adept at expressing it that she was never innocent. There were many extraordinary moments in her performance. Her line never showed an angle. All curves and yearning, she was a vine, clinging to Romeo in the pas de deux or, back almost impossibly arched, a bow.

Her finest moments came in the third act, particularly in the scenes where she defied her parents. There was anger in her dancing, and pride. When she had to bourre'e in a circle around Paris at her parents' insistence, she wrenched herself up on point, a willful teen-ager. Feet that only moments before had curled like hands around Romeo's legs stiffened, becoming deliberately ugly.

As Romeo, a more pallid character, MacKenzie had fewer dramatic opportunities but expressed his love for Juliet in big, easy movements, impetuously shooting into an arabesque or dashing off extremely fast turns.

Clark Tippet's Tybalt was superb, an intelligent, sophisticated man, potentially a great leader if he could only control his anger. He drew his character so strongly that one not only mourned his death but understood Lady Capulet's ravings.