NEW YORK (AP) — NBA Commissioner Adam Silver says he “couldn’t disagree more” with comments made by Players Association executive director Michele Roberts about the league’s salary system.

Roberts told ESPN.com in an interview that the salary cap was “incredibly un-American” and that “my DNA is offended by it.”

But Silver says in a statement Thursday that a salary cap system is not unusual and has “served as a foundation for the growth of the league and has enabled NBA players to become the highest-paid professional athletes in the world.”

Roberts was elected by players in July, becoming the first woman to lead a North American sports union. Players and owners agreed to a 10-year collective bargaining agreement in 2011, and either side can opt out in 2017.