Broncos Vice President of Football Operations John Elway attends the NFL Annual Meetings at the Roosevelt Hotel in New Orleans. (Sean Gardner/GETTY IMAGES)

The NFL on Monday urged a federal judge to wait for a critical ruling by the National Labor Relations Board in the league’s labor dispute with players before deciding whether to end the lockout imposed by owners.

The filing to judge Susan Richard Nelson raised the prospect of a lockout that could continue beyond the April 6 hearing that she has scheduled on the players’ request to end the lockout. One NFL official said Monday that he doesn’t expect the NLRB to complete its investigation for at least a few more weeks. The entire process, including appeals, could last a year, he said.

A spokeswoman for the NLRB declined to comment Monday on how long the investigation might take.

The NFL also contends in its 57-page filing that Nelson, whose court is in St. Paul, Minn., should reject the players’ request for a preliminary injunction to lift the lockout because she lacks the authority to issue one under federal labor law.

The players dissolved their union March 11, filed an antitrust lawsuit against team owners and asked the Minnesota court to lift the lockout. Owners locked out the players the next day.

In February, the league challenged the validity of decertifying the union in an unfair labor practice charge to the NLRB that accuses the NFLPA of failing to bargain in good faith because it was more interested in decertifying and filing antitrust litigation. The union has denied the allegations.

In its court filing Monday, the NFL urged Nelson to wait for a decision by the NLRB.

“If the Board finds such a violation, it will issue an order requiring the union to return to the collective bargaining table,” the NFL argued. “. . . The Court must stay this case pending the outcome of the Board proceedings.”

The league also wrote in its court documents that the lockout is “unquestionably lawful and permitted by federal labor law.” The players’ case does not fulfill the requirements for an injunction, the league’s lawyers wrote, because the players are not likely to succeed on the merits of their antitrust claim and the players cannot demonstrate they would suffer irreparable harm if they aren’t granted an injunction.

The court filing came as owners met Monday at a hotel in New Orleans. Talks between the league and players have been on hold since negotiations collapsed 11 days ago.

League officials have said that because they don’t recognize the validity of the players’ union decertification, they would be willing only to resume collective bargaining with the union.

But the players contend that the union no longer exists and any talks with the league would have to be held with the players’ attorneys in the antitrust lawsuit.

“We are not interested in negotiating with the lawyers for the plaintiffs,” one person on the owners’ side of the dispute said Monday, speaking on the condition of anonymity because of the pending litigation.

If Nelson ends the lockout and the NFL cannot win a stay of her decision, the NFL would have to put work rules in place and reopen for business while it appeals to a higher court.

Sources have said the league would apply the same rules used last season, which was played without a salary cap.

Jeff Pash, the NFL’s lead negotiator, declined to confirm that Monday, saying that league officials “talked about the full range of alternatives” with the owners.

The league meeting is scheduled to conclude Tuesday with the owners considering proposals to make kickoffs safer and subject all scoring plays to instant replay review.

The competition committee’s proposed rule changes on kickoffs would have the kick being taken from the 35-yard line instead of the 30. The ball would be placed on the 25-yard line instead of the 20 on a touchback on a kickoff. And prospective tacklers would be allowed no more than a five-yard running start before the kick.

That proposal could change before owners vote on it Tuesday. Coaches raised objections Monday, particularly to the notion of the touchback being on the 25-yard line.

Atlanta Falcons President Rich McKay, the chairman of the competition committee, acknowledged that coaches had raised concerns and said: “I don’t blame anybody for pushing back.”

But McKay also said: “This is 100 percent about safety.”

Members of the competition committee were scheduled to meet Monday night and it was possible they would tweak the proposal. McKay said he still expected the owners to vote on a kickoff-related proposal Tuesday. Any rule change would have to be ratified by at least three-quarters of the owners to be enacted.

The committee also has proposed rewording the rules protecting defenseless players from hits to the head. The revisions would expand the protection given to a receiver who’s in the act of making a catch, and would ban tacklers from launching themselves at ball carriers in most instances.

One previously undisclosed proposal would require a team to have league approval to have a home field any color other than green.