NFL Commissioner Roger Goodell, left, and DeMaurice Smith, executive director of the decertified NFL Players Association, rejoined the talks Thursday, along with groups of owners and players. (Brian Blanco/Associated Press)

Negotiators for the NFL and locked-out players moved closer Thursday to resolving the economic issues at the heart of the sport’s nearly four-month shutdown, according to several people not involved in the talks but with knowledge of them.

If completed, an agreement on how to divide the sport’s revenues would be a major step in their bid to complete a deal to end the labor lockout in the coming days.

There still were potential obstacles that could derail negotiations even as the two sides closed in on an agreement on a system to split the NFL’s burgeoning revenues, several of those familiar with the negotiations said. They spoke on the condition of anonymity because of the sensitivity of the deliberations. The negotiations have come close to unraveling previously and that could happen again, they cautioned.

The two sides met into the night Thursday in New York, breaking for the night shortly before 11 p.m. Full negotiating teams for the league and players gathered for the first time this week after meetings Tuesday and Wednesday consisted of attorneys and staff members only.

The players who are the named plaintiffs in an antitrust lawsuit against the NFL’s franchise owners were briefed on the talks in a conference call late Thursday with negotiators for the players’ side.

The focus of Thursday’s meeting was the core financial issues beginning with how the league and players will divide the sport’s annual revenues, currently about $9.3 billion and expected to rise sharply in coming seasons.

Difficult issues such as a rookie pay system and benefits for retirees are closely related to the core division-of-revenues issue. There also are other matters, such as how free agency would work, that must be resolved.

The talks were scheduled to continue at least through Friday, with tentative plans to go through the weekend if needed. The court-appointed mediator for the two sides, Chief Magistrate Judge Arthur J. Boylan, is scheduled to leave Saturday on vacation, but the talks could continue without him.

Negotiations have been precarious and nearly collapsed late last week. That near breakdown came during a set of negotiations in Minneapolis. But negotiators for the league and players repaired the rift during a late-night meeting last week, setting the stage for this week’s talks and the latest negotiating push to complete a deal.

An agreement between the league and players on how to share revenues would be a key first step toward completing a handshake deal for an overall accord to end the lockout. Many observers throughout the sport seem convinced that if the split-of-revenues issue is resolved, the other issues in the dispute would fall in line quickly.

The two sides apparently planned to focus Thursday and Friday on the key economic issues, hoping to resolve them before moving on to other matters.

An agreement on the central economic issue probably would result in the players receiving a little less than half the sport’s revenues under a salary cap system.

Players have been locked out since March 12 and, with time dwindling to salvage a full preseason, those in the industry are eager for a resolution.

Agent Drew Rosenhaus wrote Thursday on Twitter that “now is the time to close out” a deal and the “next [two] days will be pivotal. Let’s get this deal ironed out [and] get back to football!”

NFL Commissioner Roger Goodell and DeMaurice Smith, the executive director of the NFL Players Association, rejoined the talks Thursday, along with groups of owners and players. The owners were represented by the New York Giants’ John Mara, the New England Patriots’ Robert Kraft, the Pittsburgh Steelers’ Art Rooney II, the Kansas City Chiefs’ Clark Hunt and the Dallas Cowboys’ Jerry Jones.

The players’ group included Domonique Foxworth, Jeff Saturday, Kevin Mawae, Charlie Batch and Sean Morey.