With the NFL on the brink of its first work stoppage in nearly a quarter of a century, Commissioner Roger Goodell and union head DeMaurice Smith met at a federal mediator's office Friday, the day the league's twice-extended labor contract was set to expire.

Goodell was joined by nine of the 10 members of the owners' labor committee, along with various league executives and lawyers. Smith walked over from the NFL Players Association's nearby headquarters with about 20 people, including New Orleans Saints quarterback Drew Brees and several other current or former players.

Friday was the 16th day of negotiations since Feb. 18. The collective bargaining agreement originally was scheduled to run out last week; another extension was possible.

"We're going to head inside today, try to get some work done," Smith said.

Said lead NFL negotiator Jeff Pash: "We'll do our best."

But with little apparent progress on key economic issues — how to divide more than $9 billion in annual revenues, and the union's demand for full financial data — and a public series of back-and-forth barbs Thursday night, there was a chance talks would break off.

That could lead to the union dissolving itself, meaning players would give up their rights under labor law and instead pursue antitrust cases in court, and the owners could impose a lockout. Both actions could threaten the 2011 season of a sport at the height of its popularity. The past two Super Bowls are the two most-watched programs in U.S. television history.

The NFL hasn't lost games to a work stoppage since 1987, when a strike shortened the season and some games included non-union replacement players.

The current CBA was agreed to in 2006. It included an opt-out clause for each side, and the owners exercised it in May 2008.

There have been various issues discussed during the current negotiations, including the owners' push to increase the regular season from 16 games to 18; a rookie wage scale; and benefits for retired players.

Truly, though, the dispute centers on money: how to divide the billions in revenues, how much of that should go to owners off the top to cover certain costs, and the union's insistence on what it calls "financial transparency."

Under the old CBA, owners received an immediate $1 billion to go toward operating expenses before splitting remaining revenues with players. Owners initially tried to add another $1 billion to that. Although they have lowered the upfront figure they want — at least down to an additional $800 million — Smith said it is still too much.

"To our fans - I give you my word that we as players are doing everything we can to negotiate with the NFL towards a fair deal," Brees wrote on his Twitter feed Friday morning.

He continued: "The NFL brought this fight to us - they want $1 billion back, we just want financial information to back up that request."

And more: "We have a responsibility to our players - past, present, and future, to advance this league forward, not take 3 steps back."

The labor committee members present Thursday and Friday were Jerry Richardson of the Panthers, Pat Bowlen of the Broncos, Jerry Jones of the Cowboys, John Mara of the Giants, Art Rooney II of the Steelers, Clark Hunt of the Chiefs, Mark Murphy of the Packers, Dean Spanos of the Chargers and Mike Brown of the Bengals. Eagles president Joe Banner and Redskins general manager Bruce Allen also were there both days.

The only missing member of the key league group was Patriots owner Robert Kraft, who is part of a delegation visiting Israel with Massachusetts Gov. Deval Patrick.

On Thursday, the union complained that none of the owners met with any of the players on hand.

The rhetoric rose as the clock ticked down Thursday night.

"I've said it many times: If both sides have an equal commitment to getting this deal done, it will get done," he said. "I don't know if both sides have an equal commitment. ... Obviously, we have the commitment."

When that was relayed to NFL Players Association spokesman George Atallah, he responded with an e-mail to The Associated Press that said: "Jeff Pash was part of an executive team that sold the networks a $4 billion ticket to a game they knew wouldn't be played. The only thing they've been committed to is a lockout."

That is a reference to a court ruling last week, when the federal judge overseeing NFL labor matters sided with players in their case accusing owners of improperly negotiating TV deals to prepare for a work stoppage.

Smith then went back to the mediator's office to respond to Pash's statement himself.

"We have been committed to this process. But for anyone to stand and turn to the American people and say they question that?" Smith said. "Look, I understand that there's probably some things Jeff Pash just has to say, but this is the truth: We know that as early as March of 2009 ... the National Football League engaged in a strategy to get $4 billion of television money ... even if the games weren't played."

The public acrimony between the sides temporarily had been tamped down in recent weeks, because mediator George Cohen asked the league and union to stay silent about the talks.

"Things can come together quickly," Pash said Thursday night. "Things can fall apart quickly."