NEW YORK (AP) — The Major League Baseball Players Association is attempting to unionize minor leaguers, reversing decades of opposition.

The players’ association said Monday it is circulating union authorization cards among players with minor league contracts to form a separate bargaining unit from the big leaguers.

While the average major league salary is above $4 million, players with minor league contracts earn as little as $400 a week during the six-month season.

“The working conditions facing these players have been nothing short of offensive,” union head Tony Clark wrote in a letter Sunday to player agents. “Poverty wages, oppressive reserve rules, discipline without due process, ever-expanding offseason obligations, appropriation of intellectual property, substandard attention to player health and safety, and a chronic lack of respect for minor leaguers as a whole (to name just a few) — these cancers on our game exist because minor league players have never had a seat at the bargaining table. It’s time for that to change.”

The union’s executive board unanimously approved the minor league initiative on Friday.

Clark was not available to respond to questions, spokesman Chris Dahl said.

Signed cards from 30% of the estimated 5,000 to 6,000 minor leaguers in the bargaining unit would allow the union to file a petition to the National Labor Relations Board asking for an union authorization election. MLB also could voluntarily recognize the union representing the bargaining unit, a process that typically can occur if a majority of the unit signs cards.

The staff of Advocates for Minor Leaguers, which formed two years ago, quit and will work for the MLBPA. The union gave the minor league group $50,000 last November.

“This generation of minor league players has demonstrated an unprecedented ability to address workplace issues with a collective voice,” Harry Marino, the executive director of Advocates for Minor Leaguers, said in a statement. “Joining with the most powerful union in professional sports assures that this voice is heard where it matters most — at the bargaining table.”

Players with major league contracts, of which there are approximately 1,200, are represented by the union, which since the 1981 strike settlement also has negotiated terms for those on option to the minor leagues.

MLB raised weekly minimum salaries for minor leaguers in 2021 to $400 at rookie and short-season levels, $500 at Class A, $600 at Double-A and $700 at Triple-A. For players on option, the minimum is $57,200 per season for a first big league contract and $114,100 for later big league contracts.

In addition, MLB this year began requiring teams to provide housing for most minor leaguers.

Prodded by the minor league advocacy group, leaders of the Senate Judiciary Committee said last month they planned a hearing on the sport’s antitrust exemption.

Unionizing could limit the minor leaguers’ ability in future lawsuits. The Supreme Court ruled in the 1996 case Brown v. Pro Football Inc. that unionized industries are exempt from antitrust challenges.

The big league union had long declined to represent minor leaguers, though its labor contract specifies terms for the amateur draft and signing bonuses for amateur players. There were 128 draft picks this year who agreed to signing bonuses of $500,000 and up, including 82 for at least $1 million.

The players’ association negotiated its first collective bargaining agreement in 1966 and has gone through nine work stoppages, the latest a 99-day lockout that delayed the start of this season.

Major League Baseball and lawyers for minor leaguers agreed this year to a $185 million settlement of an 8-year-old federal lawsuit alleging violations of minimum wage laws. An early estimate is that perhaps 23,000 players could share roughly $120 million with an average payment of $5,000 to $5,500, and their lawyers will split $55.5 million.