WASHINGTON — Those optimistic about the NFL's labor talks with the players' union will point to the sides' decision to push back the bargaining deadline by a week and think, as Commissioner Roger Goodell put it:

"The fact that we're continuing this dialogue is a positive sign."

And those who are pessimistic about where this all eventually is headed will recognize that, as league lead negotiator Jeff Pash described it:

"We've got very serious issues. We've got significant differences."

That last observation has been obvious all along. Indeed, from shortly before Thanksgiving until the day before the Super Bowl in February, the sides went more than two months without sitting down in large groups for face-to-face, formal bargaining on a new collective bargaining agreement.

The sides were using this weekend to assess their positions, before resuming talks in front of a federal mediator Monday — and then they will have until the end of Friday to reach a new CBA, thanks to two extensions of the old deal. It originally was to have expired last Thursday.

What will happen 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.

After having such a hard time arranging full-scale sessions, the league and NFL Players Association have spent time at the Federal Mediation and Conciliation Service on 11 of out of 15 days. According to mediator George Cohen, the tenor of the talks has changed.

The two parties reached a "level of dialogue" and "constructive discussion" where they "fully, frankly and candidly talk to each other," Cohen said Friday.

Pash gave Cohen and his colleagues at the FMCS, a U.S. government agency, credit for that.

"What the mediators bring to the process is a structure and a discipline that wasn't always there," Pash said. "They inject a seriousness of purpose to it. And they encourage you. They keep you going."

There wasn't someone to play that role before Feb. 18, when Cohen first presided over the negotiations, only days after the NFL filed an unfair labor practice charge against the union with the National Labor Relations Board.

The sort of discourse now present was a rarity since the owners exercised a mutual opt-out clause in the CBA in 2008.

There has been plenty of acrimony along the way. When either side spoke publicly about the process, it often was to take a jab at the other side for not responding to proposals or for being unreasonable. The league would accuse the union of hoping not to get a deal done so it could dissolve and pursue an antitrust lawsuit. The union would accuse the league of hoping not to get a deal done so it could lock out the players.

Those two strategies — and the specter of the NFL's first games lost to a work stoppage in nearly a quarter-century — are set aside for the moment. But they could emerge again if things don't go well.

The extension until next Friday indicates neither side 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.

Money, not surprisingly, is what is at the center of the standoff.

One person with knowledge of the negotiations told The Associated Press on Friday 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.

—The owners' push to expand the regular season from 16 games to 18 while reducing the preseason by two games.

—Benefits for retired players.

There's another way in which money is a factor: The longer it takes to come to an agreement, the more revenues are going to start slipping away.

The league has estimated there would be a cut in gross revenues of $120 million without a new collective bargaining agreement by early March; $350 million if there's no CBA by August, before the preseason starts; and $1 billion if no new contract is in place until September. If regular-season games are lost, the NFL believes revenue losses could top $400 million a week.

"The reality is what is going to move the needle on this is the fact we are into March, when season tickets and sponsorships have to be set, and people need to make decisions to set the gross revenues," agent Peter Schaffer said. "There's urgency there."