A majority of the owners in the National Football League support locking out the players union just before the start of the regular season, unless contract negotiations improve dramatically, it was learned yesterday.

League sources confirmed yesterday that a leaguewide lockout before Sept. 12 is becoming increasingly more appealing to the owners, who want to deny the union the leverage of calling a strike once the season begins.

"We have learned by what happened to baseball," a source said yesterday. "Once the season begins, the union will have all the leverage. They'll have us where they want us.

"By letting the baseball players have part of a season, the baseball owners allowed them to build up money to prepare for a strike. If we let them go three or four games and then have a strike, we'll be, in reality, funding a strike, too.

"What would prevent a lockout? An agreement, and I don't see that happening."

The contract talks will resume here at 10 a.m. today, and the longer they drag on, the more some owners are becoming convinced that a lockout is their only option, as long as the union sticks with its percentage-of-the-gross demand. Sources said they are convinced an overwhelming majority of owners now favor a lockout.

A decision to order a lockout would be made by the six members of the Management Council executive committee: Jim Kensil, the president of the Jets; Leonard Tose, owner of the Eagles; Mike Brown, assistant general manager of the Bengals; Hugh Culverhouse, owner of the Buccaneers; Dan Rooney, owner of the Steelers, and Chuck Sullivan, vice president of the Patriots.

Although the union talks openly about striking, it has not announced a strike deadline. Some union officials say that it makes sense to strike sometime after the third regular season game, because veteran players then would be vested in the pension fund for another year.

Jack Donlan, executive director of the NFL Management Council, declined to comment on the number of owners favoring a lockout. He did say that a "lockout is a possibility because the owners are concerned about the undermining effects of a strike.

"All the owners are very interested in getting this contract settled as soon as possible. But our concern is with the players who have been promising a strike since before these talks began. And the owners wonder whether or not allowing the players to strike is in the long-term best interests of the game, fans and players."

Donlan reiterated that he will evaluate the state of contract negotiations around Sept. 8. It was learned that Donlan argued against locking the players out of training camp, as some owners favored.

"If they lock us out, their hope would be that the players would become so desperate for money that we would accept their last offer," Ed Garvey, executive director of the players association, said. "The scenario usually is that, prior to a lockout, they would place on the table an offer they'll label their take-it-or-leave-it package. The lockout would force us to take it.

"It's a gamble on their part. I think the risks are tremendous. The public certainly won't like it and we certainly won't sit there and do nothing. We are continuing to formulate plans to play games even if a lockout occurs. They can't prevent the players from pursuing a livelihood.

"What if it doesn't work and they let us back in? We still can call a strike later. It would be a last-ditch effort on their part. Anyway, no one is in charge of their store. Look what has happened to them. Pete Rozelle just gambled and lost with the Oakland Raiders. Oakland is now in Los Angeles and it's over, period. Are they dumb enough to gamble again?"

Donlan wanted to use today's bargaining session to begin negotiating some of the 31 individual contracts of players who have been represented by the union in their dealings with clubs since the collective bargaining agreement expired July 15.

But Garvey said he will not undertake such bargaining since the league has not provided sufficient information about comparable player contracts to allow the union to negotiate intelligently.

The NFLPA has filed a grievance with the National Labor Relations Board asking that the league be required to provide that contract information.

According to Donlan, two top-round draft choices, Darrin Nelson of Minnesota and Marcus Allen of Oakland, have not signed. Among the veterans still unsigned are Ed Jones of Dallas, Alfred Jenkins of Atlanta, Gary Danielson of Detroit, Leon Gray of Houston, Rob Carpenter of New York Giants, Henry Lawrence of Oakland, Ken Greene of St. Louis, Efren Herrera of Seattle and Bob Swenson, Tom Jackson and Bill Thompson of Denver.

All the veterans have the option of signing a contract for 110 percent of their 1981 salary or accepting the last offer made by their team.

"Ed Garvey has more information about contracts than any negotiator in the history of this league," Donlan said. "He just doesn't want to negotiate. It would help if he would get serious and cut out this smoke-screen stuff."