The American Federation of Television and Radio Artists and Screen Actors Guild said that they have sent out ballots on their proposed merger to the 131,000 members of both organizations.
Ballots are due back by March 30.
The mailing comes after opponents of the plan filed a lawsuit Wednesday charging SAG's board of directors with breach of fiduciary duties.
The suit also alleges that the union failed to conduct a study detailing the effects that joining with AFTRA will have on SAG's pension and health benefits.
Also read: SAG Merger Opponents File Suit to Prevent Vote
SAG filed a motion to dismiss the lawsuit Friday, but the case is expected to be heard in federal court days before the ballots are due to be returned.