By Andrew Longstreth 

NEW YORK, Jan 3 (Reuters) - As the National Hockey League and the players' union sought to negotiate the end to a long labor dispute that has jeopardized the season, proceedings in a lawsuit pitting the two sides against each other moved forward.

In a court filing on Thursday, the players asked a federal judge to dismiss a lawsuit brought by the league that sought a declaration confirming the legality of the player lockout.

The lockout has been in place since mid-September as the two sides have struggled to come to a new labor agreement. The league has canceled games up to Jan. 14, more than 50 percent of the regular season which was scheduled to start in October.

The dispute moved to court last month after reports circulated that the NHL Players' Association (NHLPA) would seek a vote from its members to proceed with a "disclaim of interest" and no longer represent players in bargaining.

Such a move would free players to file antitrust lawsuits against the league in an effort to block the lockout.

In its court filing on Thursday, lawyers for the NHLPA argued that the lawsuit filed by the league was premature and that it should be dismissed.

"They ask the Court to simply assume the outcome of events that had not yet taken place at the time the Complaint was filed, and then decree what the law would be on the basis of those assumptions," wrote lawyers for the players.

A spokesman for the NHL declined to comment on the filing.

U.S. District Judge Paul Engelmayer of Manhattan immediately responded to the players' request by issuing an order scheduling a conference Jan. 7 to establish a case-management plan for the litigation. He wrote that the goal of the plan should be to enhance "the parties' ability to resolve their disputes with dispatch."

The case is National Hockey League v. National Hockey League Players' Association, U.S. District Court for the Southern District of New York, No. 12-09133