PHOENIX -- Major League Baseball Players Association executive director Tony Clark is confident that at least 30% of minor league players will sign recently distributed union authorization cards in the coming days and weeks, paving the way for thousands more players to potentially join the organization.

"There was tremendous response," Clark told the AP on Tuesday. "That's probably not surprising."

Signed cards from 30% of minor leaguers in the bargaining unit would allow the union to file a petition with the National Labor Relations Board asking for a union authorization election, which would be decided by majority vote. Minor league players would have a separate bargaining unit from their big league counterparts.

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.

Clark said that while there's been a lot of action over the past two days, the efforts to push forward with minor league unionization have been in the works for a few years. Clark, who played 15 years in the major leagues, credited the minor league players for "finding their voice."

"This is the right time, because they say it is," Clark said.

"I think we're early in the process, albeit a lot of progress has been made in a short time," he added. "Oftentimes, these drives are anything but a straight line. We'll navigate accordingly."

MLB estimates that there are 5,000 to 6,500 U.S.-based minor leaguers at any given time, with the number increasing when new players sign each summer. It's a diverse group of players that includes teenagers and others in their 30s at the higher levels.

The 1,200 players on major league contracts are already represented by the union, which since the 1981 strike settlement, also has negotiated terms for those on option to the minor leagues. Clark stressed that if the minor league players decide to form a bargaining unit, it wouldn't siphon resources from the union's major league staff.

"We'd be looking at this as one big tent, if you will, with two different tables," he said.

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.

Clark said that if the minor leaguers decide to unionize, dues "will be minimal at most," acknowledging their current low compensation. The MLBPA declined to say how much it was spending on the drive. Clark said in an earlier statement that the cost was an "investment in the future of our game and our Player fraternity."

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.