The NFL has proposed to the NFL Players Association that a portion of players’ salaries for the upcoming season be placed into escrow, according to a person familiar with the deliberations.

The league’s proposal is based on the possibility that revenue will drop this season due to the novel coronavirus pandemic. The funds withheld would be paid to the players on a timetable determined once any revenue decline for this season is calculated. The NFLPA does not intend to agree to the proposal, according to a person with knowledge of the union’s views.

With the scheduled opening of training camps three weeks away, the league and union continue to haggle over economic and noneconomic issues. One of the unresolved health and safety issues is the use of face shields on players’ helmets. The NFL wants to make the shields mandatory in an effort to reduce the potential spread of the virus. The NFLPA wants to encourage players to wear face shields during training camp and then reevaluate based on field testing and player feedback, according to people close to the deliberations and a union memo.

The economic differences stem from the prospect of reduced revenue if games must be canceled or played in stadiums with few or no fans. The NFLPA recently estimated to agents that league revenue would drop by $3 billion this season if games are played without fans.

Players are to be paid 47 percent of league revenue this season through the salary cap system, under the terms of the new collective bargaining agreement. The salary cap for the 2020 season is set at $198.2 million. If this season’s revenue drops, the resulting reduction in players’ salaries would come via a drop in the 2021 salary cap.

The league’s escrow proposal could reduce teams’ player costs this season and potentially would smooth over a major reduction in next season’s salary cap. The funds placed in escrow eventually would be paid to the players, with the timing dependent upon what percentage of this season’s salaries are placed into escrow vs. what portion of this season’s revenue is lost. NFL Network reported that the league’s proposal is for 35 percent of this season’s player salaries to be placed into escrow.

The NFLPA probably would prefer to address any reduction in next season’s salary cap by proposing to “borrow” from future salary caps for the 2022 season and beyond, people in the league have said. The NFLPA did not respond to a request for comment.

Agent Drew Rosenhaus wrote on Twitter: “This is an absurd ask by the NFL. If anything the players deserve a bonus for playing with the added risk of contracting Covid 19 and potentially passing it on to their families.”

The back and forth between the league and union intensified a bit Tuesday morning when Cleveland Browns center JC Tretter, the NFLPA’s president, wrote in an essay posted on the union’s website that the league must adapt better to the current circumstances or risk not being able to play a complete season. He wrote that “the NFL is unwilling to prioritize player safety and believes that the virus will bend to football.”

The NFLPA is seeking to eliminate the preseason entirely, while the league wants each team to play two preseason games. The sides also differ on how training camp activities should be organized.

“Every decision this year that prioritizes normalcy over innovation, custom over science or even football over health, significantly reduces our chances of completing the full season,” Tretter wrote.

The NFL declined a request for comment. But according to a person familiar with the league’s view, the NFL believed that Tretter’s statement was misleading and that it was incorrect to characterize the NFL as not working with the NFLPA on health and safety issues or following the recommendations of the joint medical committee.

The league and union also are deliberating over details of the coronavirus testing program for players. The league sent a treatment plan to teams Friday as part of a set of protocols for training camp and the preseason.

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