NEW YORK, N.Y. - The NHL's labour talks remained on track after a marathon day of negotiating ended with the NHL Players' Association electing to let a self-imposed deadline to file a "disclaimer of interest" pass.

The sides were due to return to the league office nine hours after talks broke off early Thursday morning to resume discussions with U.S. federal mediator Scot Beckenbaugh, who has rejoined the process in recent days.

Even though gaps remained on some key issues, there was a faint hint of optimism in the air. Had the NHLPA's executive board elected to file the disclaimer prior to midnight ET on Wednesday, talks would almost certainly have broken off. Instead, both the league and union remained committed to trying to hammer out a deal that would save a shortened season.

"There's been some progress, but we're still apart on a number of issues," said commissioner Gary Bettman. "As long as the process continues I am hopeful."

His counterpart, NHLPA executive director Donald Fehr, echoed the sentiment that movement had been made at the bargaining table but was vague about how long negotiations will continue in the manner they've been going.

The union still has the option to poll players on whether they'd support a "disclaimer of interest" — the first one passed overwhelming last month — and a source indicated that it remains a viable option if a deal isn't struck soon.

"The parties moved closer together on some issues," said Fehr. "There is still a ways to go if an agreement can be reached. We'll consider where we are in the morning and we'll figure out what to do next."

Among the issues still to be ironed out are pension funds and the salary cap for 2013-14, which is particularly important since the sides have already agreed on a 50-50 split of revenue. The league continues to look for a US$60-million cap while the union is asking for one at $65 million, according to sources.

One item that hasn't cropped up in discussions is a cap on escrow, a potentially divisive topic that some thought the NHLPA might seek. The union's proposals haven't touched on that subject, according to a source.

With a deadline looming to save the season, the sides have engaged in a busy few days of negotiations. Proposals were traded back and forth across the table all week and representatives from the NHL and NHLPA met on and off over roughly 15 hours on Wednesday.

"We've had a long day with lots of meetings," said Bettman.

Both sides have largely closed ranks at a critical stage in negotiations, with only small tidbits of information leaking out. The league has set a Jan. 11 deadline to preserve a 48-game season and there was still some hope that 52 games could be squeezed in if an agreement was reached this week.

That is looking less and less likely.

However, it remained a small possibility with the union continuing to represent the players in negotiations. Had the NHLPA elected to dissolve, it would have opened the doors for players to file antitrust lawsuits against the league. More traction will need to be made in talks to keep them from going down that road.

"All I can tell you about that is the players retain all the legal options they have always had and we don't talk about legal matters," said Fehr.

If the league is concerned about the possibility, it hasn't shown any hint of it. Bettman has continually downplayed that option when asked about it.

"The word 'disclaimer' has never been — has yet to be — uttered to us by the players' association," he said. "When you disclaim interest as a union you notify the other side. We have not been notified."

Instead, the focus has remained on negotiations.

The lockout hit 110 days on Thursday and more players continued to make their way back to North America in anticipation of a potential season. Ottawa Senators forward Jason Spezza was the latest to leave Switzerland.

The biggest remaining question is whether the sides are prepared to clear the final remaining hurdles.

"On some issues we agreed, on some we moved towards each other, and on some we said 'no' and I think that applies to both parties and how they've proceeded during this process," said Bettman.

"We talked about lots of things. We even had some philosophical discussions about why particular issues were important to each of us, and that's part of the process."

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