WASHINGTON -- The NFL and NFL Players Association agreed Thursday to a 24-hour extension of their current collective bargaining agreement, allowing them to continue negotiations and, according to a league source, possibly reach a longer extension.

Momentum to "stop the clock" on the CBA's expiration, which was supposed to happen at 11:59 p.m. ET Thursday, built throughout the day as the sides met for over eight hours at George Cohen's Federal Mediation and Conciliation Services office.

"For all our fans who dig our game, we appreciate your patience as we work through this," NFLPA executive director DeMaurice Smith said as he left the mediation session. "We are going to keep working. We want to play football."

Said NFL Commissioner Roger Goodell as he left: "We are working as hard as we can."

Jeff Pash, the NFL's lead labor negotiator, repeatedly praised Cohen when leaving the meeting, saying it was "a good day of work" and that the sides will come back Friday by 8:30 or 9 a.m.

"We're going to keep at it as long as it takes," Pash said.

When asked if this extension could lead to another extension, Pash said: "We'll see."

The union and league will have separate sessions to start Friday, sources told NFL Network's Albert Breer. The league will meet with Cohen while the union's negotiating team likely convenes at its nearby office and awaits word on what comes out of the NFL's talks, then proceed accordingly.

The sides hope to avoid the first work stoppage since 1987 for a league that rakes in $9 billion annually. The labor unrest comes as the NFL is at the height of its popularity, breaking records for television ratings: This year's Super Bowl was the most-watched program in U.S. history.

During the one-day extension, teams still can operate under the terms of the current CBA, according to a league source. Teams can release players up to the Friday waiver deadline and sign existing free agents or extend player contracts.

The CBA was extended during the 2006 labor negotiations, and a deal ultimately was reached. The NFLPA was prepared to decertify Thursday in an attempt to prevent a lockout if no deal or extension was reached.

The NFLPA decertified in 1989, then formed again in 1993.

Sources said the NFLPA still isn't willing to rule out decertification -- the deadline to file is now 4 p.m. ET Friday -- just as the NFL is certain not to rule out the possibility of a lockout.

If the union eventually decertifies, sources told Breer that quarterbacks Tom Brady, Peyton Manning and Drew Brees would serve as the lead plaintiffs in any potential antitrust lawsuit filed against the league.

The union has asked league owners to open their books and reveal more data about expenses and revenue. After meeting with Cohen on Wednesday night, a source said, Goodell and his negotiating team were more inclined to reveal additional financial information at Thursday's session.

But Washington Redskins player representative Vonnie Holliday cautioned that the sides are "still apart" on a pact to replace the current CBA.

"I don't see how we can be that close right now unless somebody is going to pull a rabbit out of the hat," he said. "I just don't see it."

While the league and players' union met for a 10th day with Cohen, even President Barack Obama weighed in when asked if he would intervene in the dispute.

"I'm a big football fan," Obama said, "but I also think that for an industry that's making $9 billion a year in revenue, they can figure out how to divide it up in a sensible way and be true to their fans, who are the ones who obviously allow for all the money that they're making. So my expectation and hope is that they will resolve it without me intervening, because it turns out I've got a lot of other stuff to do."

Besides Goodell, also on hand for the NFL were Pash, outside counsel Bob Batterman, New York Giants owner John Mara, Green Bay Packers president Mark Murphy, Redskins general manager Bruce Allen and several other league executives. Mara and Murphy are members of the league's labor committee, which has the authority to call for a lockout if a new agreement isn't reached.

Joining Smith at the mediation session Thursday were union president Kevin Mawae, New Orleans Saints quarterback Drew Brees, Indianapolis Colts center Jeff Saturday, Pittsburgh Steelers backup quarterback Charlie Batch and several others, including current and former players.

The biggest sticking point all along has been how to divide the league's revenues, including what cut team owners should receive up front to help cover certain costs, such as stadium construction. Under the old deal, owners received about $1 billion off the top. They entered these negotiations seeking to add another $1 billion to that.

Among the other significant topics: a rookie wage scale; the owners' push to expand the regular season from 16 games to 18 while reducing the preseason by two games; and benefits for retired players.

Since the 1987 players' strike that shortened the season to 15 games -- with three of those games featuring nonunion replacement players -- there has been labor peace in the NFL. The foundation of the current CBA was reached in 1993 by then-Commissioner Paul Tagliabue and union chief Gene Upshaw. It has been extended five times as revenues soared, the league expanded to 32 profitable teams, and new stadiums were built across America to house them.

The contract extension reached in 2006 was the final major act for Tagliabue, who then retired, succeeded by Goodell. An opt-out clause for each side was included in that deal, and the owners exercised it in May 2008 -- three months before Upshaw died.

Smith replaced Upshaw as the union's leader in March 2009.

*NFL Network's Albert Breer and The Associated Press contributed to this report. *