Dan Graziano says that NFL owners have approached the players union about negotiating an extension to the current collective bargaining agreement, but that the owners would have to come to the table with something dramatic to interest the union. (1:16)

NFL owners have approached the NFL Players Association several times in recent months about negotiating an extension to the current collective bargaining agreement, and they plan to initiate those discussions again soon, sources close to the situation told ESPN's Dan Graziano.

One reason the owners want an extension is because they have exhausted all of the stadium credits that were negotiated in the 10-year deal with the players that was signed in 2011. The league is interested in trying to secure money to help fund a stadium in Las Vegas for the Oakland Raiders and possibly another facility in San Diego, sources said.

The NFLPA would listen to the league's overtures, but it's likely the players would require somewhat significant concessions from the owners to agree to an extension at this point. It's also unclear what types of concessions would prod the players to the negotiating table. For example, the majority of players do not feel strongly enough about the commissioner's control over discipline to make it a major negotiating topic.

The Las Vegas stadium project is one reason the league is interested in getting an extension done sooner rather than later.

On Friday, the Nevada Legislature signed off on a plan to use $750 million in public money to build a stadium for the Raiders. The plan would raise hotel taxes by up to 1.4 percentage points in the Las Vegas area to fund a convention center expansion and build a 65,000-seat domed stadium.

Raiders owner Mark Davis has pledged $500 million toward the stadium, $200 million of which would come from an NFL loan. Before the Raiders can move to Las Vegas, however, the team must apply for relocation with the NFL and get a three-fourths majority vote by owners to allow the franchise to move.