In what could be a harbinger of labor strife to come, the WNBA Players Association said it filed an unfair labor charge with the National Labor Relations Board late Wednesday against the New York Liberty and the WNBA for barring union officials from meeting with Liberty players at Madison Square Garden.

WNBA Players Association director of operations Pam Wheeler said she was asked to surrender her season credential after Tuesday night's game between the Liberty and the Orlando Miracle, and was advised that union officials would not be allowed to meet with Liberty players before or after games and practices at the arena.

"In the locker room after the game, they told me that they'd like to have my (season) credential back," said Wheeler, who refused to surrender it until a request was submitted in writing. "For some reason, the Liberty has radically changed their policy regarding union access to the workplace. We think this constitutes illegal conduct under the National Labor Relations Act."

A Liberty spokesperson declined comment and WNBA spokeswoman Maureen Coyle said the league would reserve its reaction until it had a chance to review the grievance. WNBA Players Association spokesperson Dan Wasserman said a copy of the union's grievance was faxed to the National Labor Relations Board late Wednesday afternoon. Original copies of the document, he said, were sent to the NLRB, WNBA and Liberty by overnight courier.

After reviewing the charge Thursday, the WNBA referred questions to the Liberty. A Liberty spokesperson said only, "It was a misunderstanding and it's being worked out."

Earlier Wednesday, Wheeler and NBA Players Association head Billy Hunter were scheduled to meet with Liberty players at Madison Square Garden. But team officials told the union leaders they could hold meetings at the Players Association's office, not at the arena where the players practice and play, Wheeler said.

According to Wasserman, Liberty general manager Carol Blazejowski later confirmed to Hunter that the team did not want union representatives conducting meetings with players at the arena.

A week ago, WNBA Players Association president and Seattle Storm guard Sonja Henning (who has since been traded to the Houston Comets) told reporters that players had "discussed the idea of getting comfortable with a strike." The league's collective bargaining agreement expires at the end of the season and players are not happy with their current salaries which, according to Wheeler, equal less than 15 percent of the league's revenue.

"It's awfully strange that we've been given open access to the facilities to all the teams with little problem, and now that we are on the verge of bargaining there is a problem," Wheeler told ESPN.com. "Our players are prepared to work with the league to ensure its success and now it seems like they are being retailiated against and can't exercise their simple right to meet."

Darren Rovell, who covers sports business for ESPN.com, can be reached at Darren.rovell@espn.com