MLB Commissioner Rob Manfred is set to introduce the new rule in early February, a person with knowledge of the matter said.
The rule would be effective in March, but the rule could be changed.
It would take effect the day before the MLB All-Star Game in Houston.
Manfred and MLBPA President Larry Lucchino, who are in Houston for the event, have said the new policy would allow players to play during the season.
But that would only be a temporary measure, according to the person, who spoke on condition of anonymity because the agreement hasn’t been finalized.
The MLBPA declined to comment.
The new rule would allow the union to negotiate an extension of its collective bargaining agreement with the league, which expires at the end of the month.
It could also allow players who have signed their first-year contracts before the new year to earn up to $300,000 annually.
MLBPA officials said they hope to make a deal before the All-Stars start their summer schedule.
They have previously been trying to get players to agree to pay up to the new rate, but those negotiations have fallen through.
The league has already increased the pay for rookies by $25,000.
But Manfred said the union could push to extend the new salary cap to $150,000 for the first two years of the deal, which would be phased in over three years.
Managers are also expected to receive a bonus based on the number of wins the league wins.
The increase in pay is a big win for the players, who have historically been paid below league minimums.
Manifold has called the salary cap “a fair deal” for players, and MLB had previously agreed to a similar cap.
But MLBPA Vice President Mark Shapiro said last week that he believes the new wage increases were not fair to the players and should be rejected.
Manitold has said that the cap was meant to keep players from getting too rich, but players have struggled to get by.
The pay increase was a part of a $100 million contract for new team owners that will be made public this week.
It includes an increase in players’ base salaries and the signing bonus.
Maniwold has proposed adding $10 million to the bonus.
A person familiar with the talks said Manfred agreed to the increase in base salary because it would give the union more flexibility to negotiate its own pay increases and better protect the players’ jobs.
The union will also be allowed to negotiate pay increases for its agents, managers and other employees.