Alessandra Ferri:ciao, London, hi, New York!

Fresh from morning class in a pink track suit, wispy tendrils of hair framing her tiny face, the Italian-born ballerina hopped onto a battered couch and chatted freely about her future -- in the United States. One of the most popular, best-known ballerinas in Britain today, Alessandra Ferri recently signed a contract to join the American Ballet Theater (ABT) in New York. She makes her debut there tomorrow night as Juliet to Kevin McKenzie's Romeo.

Miss Ferri, a graduate of the Royal Ballet Upper School and a prizewinner at the Prix de Lausanne in 1980, has had much exposure on television as well as on the stage. Her supple, malleable body, her fine technique, and her musicality have earned her splendid reviews. Veteran London critic Mary Clarke wrote in the monthly publication Dancing Times three years ago, when the dancer was 18: ``Goodness, she has everything going for her: technique, temperament and wonderful eyes.''

Since then she has gained particular recognition for her interpretations of roles by Sir Kenneth MacMillan, principal choreographer of the Royal Ballet Company, who now also divides his time between the Royal Ballet and the ABT. Ferri has been acknowledged as his muse in recent years. He has created several ballets for her. So is she going to New York to follow him?

Sitting in the red-brick building of the Royal Ballet's Upper School, Ferri gave other reasons for leaving her prestigious position here to head across the Atlantic. ``I'd like to dance more classical roles than the Royal Ballet is doing at the moment,'' she said in a soft voice, slightly accented with her native Italian. ``I would love to try Don Quixote and bring out Kitri's character, and ABT has a production in its repertoire. I'm hoping to do Giselle, which the Royal Ballet hasn't done since 1982.' '

Her brown bush-baby eyes grew even larger. ``And there's the opportunity to work and dance with Misha [Baryshnikov],'' she went on (although she will have to wait to partner him, since recent knee surgery prevents him from dancing this fall).

``I'm a great admirer of the Russian technique, and I'll always take class with a Russian teacher whenever possible.''

Her contract with ABT is for one year, but the impression here is that the lure of America will keep her away from London longer, except for possible guest appearances.

Ferri also feels that the ABT offers different teaching and training. She wants to travel and broaden her experience while young.

As it happens, her role in Sir Kenneth's version of ``Romeo and Juliet,'' which served as her farewell performance in London Aug. 2, will also be her New York debut.

MacMillan's choreography suits her talents perfectly: very much alive, charged with emotion. Ferri is able to demonstrate his style with her seemingly boneless body and fluid movements, which any gymnast would envy.

``I admire the way he works,'' she told me. ``He comes into the studio fully prepared with a basic outline of what he wants, but not the final choreography. He explains the background and the pattern, but leaves it to the dancer to demonstrate the most natural movement.

``We work together with him until he is satisfied.'' She prefers this method of creating to that of choreographers who arrive with every step completed.

MacMillan's recent ballets have been controversial. They have been criticized in ballet circles here in London for their emphasis on psychological and degrading elements. ``Valley of Shadows,'' for instance, based on the story of ``The Garden of the Finzi-Continis,'' contains brutal scenes in a Nazi concentration camp. And ``My Brother, My Sisters'' has overtones of incest and murder.

Ferri defends MacMillan, saying that he recognizes the ``inner feelings of today's society'' and that he makes ``intense statements with his theatricality.''

MacMillan designs roles for fearless ballerinas. In ``Manon,'' performed recently, Ferri threw herself, often literally, at partner Wayne Eagling. At other times she was manipulated like putty -- pulled, turned, and lifted, often upside down -- but always maintaining self-control and elegance.

Last winter she was invited to work with Franco Zeffirelli in his first-ever, and controversial, ballet production of ``Swan Lake,'' at La Scala in Milan. Among many who came was Mikhail Baryshnikov, who raised the prospect of New York with her.

How will this young ballerina fare with the ABT and New York audiences?

The feeling in London is that she will do very well. She is coming in at the top, with established credentials, and will debut in a ballet in which she has already been acclaimed a star, and choreographed by the man who molded her style.

Audiences in London will sorely miss her.