Writing on Instagram, Zegler said she was "honoured" to have been cast in the role, having only ever played Maria in a high school musical.
West Side Story is also largely based on William Shakespeare's Romeo and Juliet, and it features a star-crossed romance between Tony and a girl named Maria. As a Colombian-American, I am humbled by the opportunity to play a role that means so much to the Hispanic community, ' she gushed.
"I am so thrilled to be playing the iconic role of Maria alongside this awesome cast", Zegler told Deadline.
"I send a huge thank you to everyone who helped make this incredible dream a reality - I never could've done it alone", she continued, calling out the cast members whom she is "so honored" to work alongside "in telling this impeccably poignant story".
"I simply can not wait to get on set to work with this group of young actors", said Moreno, who won the Best Supporting Actress Oscar for her role as Anita in the 1961 film.
West Side Story, with music by Leonard Bernstein and lyrics by Stephen Sonheim, was first performed on Broadway in 1957.
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Kelly's lawyer, Steven Greenberg , claims that there hasn't been any sort of illegal acts committed on R. There's a version of the song that pairs Gaga with singer Christina Aguilera , instead of R.
Veteran performer Rita Moreno will play Valentina, an expanded version of the character Doc, the owner of the store in which Tony works.
After news of her casting broke, Zegler added on Twitter, "I could say so many things but all I can muster is thank you".
"I am so thrilled to be playing the iconic role of Maria alongside this incredible cast", said Zegler.
Zegler has been posting her covers of her favourite songs on YouTube for the past few years, amassing more than 84,000 subscribers.
"This role means the world to me and I can not wait to dance with you on set", the 87-year-old actress wrote on Twitter.
Spielberg's adaptation of the film is set to start production this summer.