LOS ANGELES (REUTERS) - The producers of a Broadway adaptation of Harper Lee's classic novel To Kill A Mockingbird on Monday (April 16) sued the author's estate saying the premiere cannot go ahead as scheduled and the production may have to be scrapped entirely unless a legal dispute is settled soon.

To Kill A Mockingbird is set to officially open on Dec 13 with previews beginning on Nov 1 in New York. But a representative of Lee's estate sued last month claiming Oscar-winning writer Aaron Sorkin's script deviates too much from the beloved 1960 novel about race relations in the Depression-era US South.

The lawsuit "has rendered it impossible for the play to premiere as scheduled in December 2018, and unless this dispute is resolved in the immediate future, the play will be cancelled", the court documents filed in US District Court in Manhattan said.

Rudin's countersuit accuses Lee estate representative, Tonja Carter, of not raising objections to the script until six months after it was submitted to Lee's literary agent in August last year.

It also asks for damages of no less than US$10 million (S$13 million) and says Carter's lawsuit has "rendered it impossible" to raise the millions in funds it says it needs before the play opens.

Carter did not immediately respond to messages seeking comment.

In her March lawsuit, Carter alleges that Sorkin, the creator of Emmy-winning TV series The West Wing, added two characters to the script and that he told trade magazine Playbill that the book as written "doesn't work at all" as a play.

The script also "did not present a fair depiction of 1930s small-town Alabama" by tying it to today's social climate and portrayed protagonist Atticus Finch as initially naive to racism, according to the lawsuit.

In response, Rudin argues the play is defined by its live stage production and not its script.

It offered to perform its adaptation at the courthouse with full cast that stars Jeff Daniels as Finch so a judge could determine if the play departed from the spirit of the novel.

Rudin, who paid US$150,000 for the stage rights to the novel, is a major Broadway and Hollywood producer, having won an Oscar and multiple Tony Awards.

Lee died in 2016 at age 89.

To Kill A Mockingbird was met with high praise on its publication, winning the Pulitzer Prize and earning Gregory Peck an Academy Award for best actor in an acclaimed 1962 screen adaptation.