The president of the Broadway stagehands union is telling other unions on Broadway that they are “under attack” by a group of theater owners who have announced they will begin imposing portions of its final contract offer starting Monday, according to a letter obtained by The New York Sun.

“We stand ready to defend ourselves from the implementation of unsafe, unsound, and unacceptable work rules that the producers are threatening to enact,” the letter, which was distributed yesterday afternoon in theaters on Broadway to members of the other 13 unions on Broadway, stated.

A source from the theater group, the League of American Theaters and Producers, said the allegations were “completely false,” adding: “The league is not going to compromise safety.” The source requested anonymity.

The league and the union, Local One, have been at odds since they submitted what they said were final offers on October 9, arguing over whether stagehands should be paid for the work they physically do, as the league argues, or whether a theater can hire stagehands daily regardless of whether work is available.

Over the weekend, shows will continue on Broadway. It may be a dark week ahead, though, should the stagehands’ union vote to authorize a strike on Sunday and the league impose portions of their final contract offer on Monday.

The two parties say they remain committed to further negotiations and to avoiding a strike by the union or a lockout by the theaters, yet neither has announced dates for those talks.

The Nederlander Organization, which represents nine Broadway theaters, announced through Local One yesterday that it would not impose the league’s work rules on Monday. The theater had a separate contract with the union and was sitting at the negotiating table as an observer. The league represents two New York theater owners, the Jujamcyn and the Shuberts, which account for 22 of the 39 Broadway theaters that would impose the work rules.