WASHINGTON -- The NFL and NFL Players Association are discussing the subject of "stopping the clock" on the current collective bargaining agreement to allow more time to negotiate, sources with knowledge of the situation said Thursday.

Doing so would allow the sides to continue discussing a new deal beyond Thursday's 11:59 p.m. ET deadline and would, in essence, begin a period of no football activity -- halting any player transactions.

According to NFL Network's Albert Breer, the NFL offered the extension of the CBA deadline, but the union wants the league to more thoroughly demonstrate that it's serious about negotiating in good faith toward a deal. A source said the union finds the league's current extension offer "unsatisfactory," because the owners won't go with "language to ensure progress and not just a delay of game."

Both parties in the room Thursday can approve the idea of "stopping the clock" without further approval from people on their sides.

A time extension or "stopping the clock" occured during the 2006 labor negotiations, and a deal ultimately was reached. The NFLPA also is prepared to decertify Thursday should there be no deal or extension.

The union has been asking league owners to open their books and reveal more economic data about expenses and revenue. After meeting with mediator George Cohen on Wednesday night, the source said, NFL Commissioner Roger Goodell and his negotiating team were in a position where they would be inclined to reveal more financial data at Thursday's session.

There is no set time to break Thursday's talks, according to sources, though particularly in the case of "stopping the clock," the process would require a signature from Judge David Doty and paperwork that would have to be executed by late afternoon.

The labor talks even have drawn the attention of the nation's first fan -- President Barack Obama.

"You have owners worth close to a billion, players making millions. The parties should be able to work it out," Obama said in a statement Thursday. "I'm a big football fan. For an industry making $9 billion, I'd hope they can figure out how to divide it up in a sensible way. ... I hope they can come to an agreement without me having to intervene."

Goodell and the NFL's negotiating team arrived at a federal mediator's headquarters about 45 minutes ahead of NFLPA executive director DeMaurice Smith and his group.

Staring at the first pro football work stoppage since 1987, Goodell said Thursday morning, "We're working hard."

Also on hand for the NFL were lead negotiator Jeff Pash, outside counsel Bob Batterman, New York Giants owner John Mara, Green Bay Packers president Mark Murphy, Washington 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 by midnight.

"We'll stay at it as long as it takes," Pash said before the 10th mediation session at Cohen's office.

The NFL and the players' union no longer have months or weeks or days to reach a new CBA. If they don't get it done now, a work stoppage is almost a certainty. America's most popular sport could see its 2011 season jeopardized.

Neither side is making optimistic proclamations.

"We're talking," union president Kevin Mawae said Wednesday. "It's better than not talking."

Are they making progress that could lead to a settlement in a dispute that involves $9 billion in revenues?

"I never have expectations, except to have A, B, C, D and E, and to always plan for F," Indianapolis Colts owner Jimmy Irsay said. "It changes. A chessboard that moves around and things happen at unusual hours."

The owners didn't spend much time Wednesday discussing where the negotiations stood, cutting their planned two-day meeting to a three-hour affair at a suburban hotel. New England Patriots owner Robert Kraft and Dallas Cowboys owner Jerry Jones, also members of the labor committee, headed home rather than stick around for further talks with the union.

"We can't comment, and even more so, we're certainly still involved in our dialogue, and so there is no comment," Jones said.

Two people with knowledge of the NFL Players Association's plans told The Associated Press that the union was prepared to decertify Thursday, barring a last-minute breakthrough. That action means the union no longer would represent the players, who would give up their rights under labor law and instead take their chances in court under antitrust law. The people spoke on condition of anonymity because the union hadn't made its plans public.

There was a flurry of activity Wednesday: a four-hour mediation session attended by all 10 members of the owners' labor committee, Mawae and New Orleans Saints quarterback Drew Brees; the three-hour owners meeting at a hotel 25 miles away in Chantilly, Va.; a one-hour meeting of the league's labor committee immediately after the owners broke up; the cancellation of another planned gathering of owners Thursday; and a private visit with Cohen starting at 8 p.m. by Goodell, two top league lawyers, Mara and Murphy.

Mara -- the first owner to attend the nine days of mediation, on Tuesday -- and Murphy left at 9:30 p.m., followed shortly by Goodell, Pash and Batterman.

"Long day," Mara said.

Asked the purpose of the 1½-hour evening meeting with Cohen, Pash said: "To speak with the mediator and get some direction."

Irsay said the owners welcomed the opportunity to be updated on negotiations, but there was little reason for them to remain in Washington as the deadline approaches.

"We had the chance to ask questions, but we didn't break with a lockout vote or anything like that," Irsay said.

Labor committee members who attended the talks Wednesday were: Mara, Murphy, Kraft, Jones, Jerry Richardson of the Carolina Panthers, Art Rooney II of the Pittsburgh Steelers, Mike Brown of Cincinnati Bengals, Clark Hunt of the Kansas City Chiefs, Dean Spanos of the San Diego Chargers, and Pat Bowlen of the Denver Broncos.

Brees, a member of the NFLPA executive committee, and Mawae hadn't attended this round of mediated negotiations, which began Feb. 18. But now all members of the union's executive committee have been present at least once.

Because Cohen told both sides to stay silent publicly about the current talks, no one has revealed any specifics about what progress might have been made.

The biggest sticking point all along has been how to divide the league's revenues, including what cut team owners should get 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.

Cohen said last week that the sides were far apart on the core issues.

By the end of Thursday, more will be known about exactly how far apart.

"I don't want to put any certainty on what this evening might bring or tomorrow might bring," Irsay said Wednesday. "It's really, truly hard to predict. These things change."

The Associated Press contributed to this report