NFL Commissioner Roger Goodell, players’ union executive director DeMaurice Smith and their bargaining teams arrived at the Washington office of the Federal Mediation and Conciliation Service shortly before 11 a.m. It was not known how long the meeting would last.

Goodell was accompanied by NFL outside counsel Bob Batterman and the league’s lead labor negotiator, Jeff Pash. No team owners were seen entering the building. About 15 minutes after Goodell showed up, Smith walked in, joined by union lawyer Richard Berthelsen, Pittsburgh Steelers backup quarterback Charlie Batch and former player Jim McFarland, a member of the NFL Players Association’s executive committee.

Goodell and Smith declined comment on their way into the meeting with George H. Cohen, the director of the FMCS, an independent U.S. government agency.

"We’re going to participate fully, and we look forward to working with Mr. Cohen," Pash told The Associated Press.

Asked what progress he expects to come from mediation, Pash replied: "We don’t know."

NFLPA spokesman George Atallah said: "We’re not going to make any comments or talk about what happens in today’s negotiating session."

Cohen announced Thursday that both sides had agreed to have him participate in talks. Mediation is not binding.

The current collective bargaining agreement expires at the end of the day March 3, and the union has said it expects a lockout to come as soon as the next day.

News of the start of mediation could be a positive sign after several months of infrequent negotiations.

The league and union went more than two months without holding any formal bargaining sessions, until a meeting Feb. 5, the day before the Super Bowl. The sides met again once last week but called off a second meeting that had been scheduled for the following day.

The most recent CBA was signed in 2006, but owners exercised an opt-out clause in 2008.

The biggest issue separating the sides is how to divide about $9 billion in annual revenues. Among the other significant points in negotiations: the owners’ push to expand the regular season from 16 games to 18 while reducing the preseason by two games; a rookie wage scale; and benefits for retired players.

Cohen was involved in Major League Soccer’s negotiations with its players’ union last year, when a possible work stoppage was avoided. Cohen also has worked with the players’ associations for Major League Baseball, helping end the 1994-95 strike as a consulting attorney, and the NBA, and was an advisor to the NHL players’ union before joining the FMCS.

The FMCS also became involved in negotiations during the 2004-05 NHL lockout, and a 2005 dispute between the U.S. Soccer Federation and its players.