Voice actors including Mass Effect’s Jennifer Hale and former Solid Snake David Hayter are threatening to strike over union contract negotiations.

Voice actors union SAG-AFTRA has been in negotiation with major publishers, including EA, Activision, Disney, and Warner Bros. over a new interactive media agreement, a contract that outlines the rights and responsibilities of voice actors.

However, negotiations have reached an impasse regarding several key points, resulting in a vote being called to determine whether union members will enact a strike.

One the contested points in the contract is a proposition to provide voice actors with a “backend bonus” for top-selling games. This bonus would provide residual royalties on games that reach two million sales, with increments in scale every two million sales up to eight million sales.

"The truth is, back end bonuses are not uncommon in the video game industry," said SAG-AFTRA in a press release.

"Last year, Activision's COO took home a bonus of US$3,970,862. EA paid their executive chairman a bonus of US$1.5 million. We applaud their success, and we believe our talent and contributions are worth a bonus payment, too."

Other stipulations include “stunt pay” for work the union deems “vocally stressful”, stunt coordinators for intensive motion-capture, and additional information for auditions within the industry.

For the strike to go ahead 75 percent of the union’s 150,000 active members would have to approve the action.

While the negotiating parties have agreed to a media blackout during voting, individuals have thrown their support behind the campaign on social media using the hashtags #performancematters and #IAmOnBoard2015.

Among the pro-strike voice actors are Jennifer Hale, David Hayter, Will Wheaton, and Borderlands and Life is Strange voice actor Ashley Burch.