WASHINGTON — The NFL and the players' union negotiated for four hours Monday before calling it a day.
    NFL Commissioner Roger Goodell, NFLPA executive director DeMaurice Smith and members of the two negotiating teams are expected to reconvene before a federal mediator on Tuesday morning.
    The current collective bargaining agreement was set to expire last Thursday, but two extensions have now pushed the cutoff to the end of Friday.
    The sides have made progress during 11 days at the offices of mediator George Cohen, but they still remain apart on key economic issues.
    What will happen this week is still anyone's guess. A deal could be reached at any time. Talks could break off. The sides could agree to yet another extension.
    By buying extra time, the league and union made it clear neither was quite ready to make the drastic move of shutting down a league that rakes in $9 billion a year and is more popular than ever. The past two Super Bowls rank No. 1 and No. 2 among most-watched TV programs in U.S. history.
    The NFL has not lost games to a work stoppage since 1987. The current CBA was agreed to in 2006. Owners exercised an opt-out clause in 2008.
    Money, not surprisingly, is at the center of the standoff.
    One person with knowledge of the negotiations told The Associated Press last week that the NFLPA has not agreed to any major economic concessions — and that the NFL has not agreed to the union's long-held demand that the league completely open its books and share all financial information.
    The person spoke on condition of anonymity because Cohen asked everyone involved not to comment on the substance of the talks.
    The key issues all along have been:
    —How to divide revenues, including what cut team owners should get up front to help cover costs such as stadium construction and improvement. Under the old deal, owners received about $1 billion off the top. They entered these negotiations seeking to add another $1 billion to that.
    —A rookie wage scale, and where money saved by teams under that system would go.
    —Benefits for retired players.
    —The owners' push to expand the regular season from 16 games to 18 while reducing the preseason by two games.
For the players to agree to a longer regular season, they would want substantial reductions in offseason workouts, minicamps and training camp. Should they get that, and if Smith can coax, say, five extra roster spots per team (160 more jobs), perhaps the league and union could find common ground on that issue.
    "There are so many moving parts, so much that goes on," New Orleans Saints union representative Jon Stinchcomb said. "When you have these CBA negotiations, what we establish now will affect how we do business for years to come. It's more than just how to slash the pie. It's how you go to work, what your offseason will look like, benefits for former players, how protected are we when injuries come along."

    AP Pro Football Writer Barry Wilner in New York, and AP Sports Writers Brett Martel in New Orleans and Joseph White in Washington contributed to this report.