WASHINGTON — The NFL players’ union filed a collusion claim against the league’s owners Tuesday, another move as the sides near the expiration of their labor contract.

The union originally had until December — 90 days after the start of the season — to accuse teams of conspiring to restrict players’ salaries last offseason, but the league agreed to extend that deadline. The case is before Stephen Burbank, the same special master who is considering a complaint about the league’s TV contracts.