Negotiations between the major league baseball owners and players broke down today and there is the inescapable feeling that things have degenerated. Federal meidator Kenneth E. Moffett, whose settlement proposal had been accepted by the players and rejected by the owners, said, "We're still stalemated. It's getting very nasty.

"There's been some progress as far as movement is concerned," he added. "As far as the tone, it's the pits."

Moffett said he would be in touch with the parties but did not expect to call any further meetings before Monday.

Moffett conceded that his proposal for ending the 30-day-old strike was dead and said it was his guess "that we need a new format."

The talks broke down this afternoon, after the owners made it clear that they could not accept the settlement proposal Moffett presented Thursday. Marvin Miller, the executive director of the Major League Baseball Players Association, said, "They advised us through the mediator that unless we had a new proposal they did not care to meet. We accept a neutral's proposal; they reject it and when they come back, they do not address it . . . If that isn't an exercise in futility for an afternoon, then I've never had an exercise in futility."

The owners had two main objections to Moffett's plan: the level of professional compensation awarded to a team losing a premium free agent and the provision that of teams losing free agents, only those that have a worse won-lost record than the teams signing the free agents would receive professional compensation. Ray Grebey, the owners' chief negotiator, said, "It leaves two-thirds of ranking free agents without compensation and it would produce more compensation for lower-ranking players."

He also described the proposal as "ambiguous and poorly written."

But, that apparently, was not the only management complaint about the proposal. There was some feeling among management sources that the proposal was heavily proplayer, raising questions about its origin. Grebey reportedly told some reporters that he believed the proposal was written by Miller. Asked about the reports, Grebey said, "I have no comment. You can make your own decision."

Miller said, "This business of attempting to cast doubt on the impartiality of the mediator . . . is a low and scurrilous tactic."

Moffett said the proposal had been drawn up by himself, and Nancy Broff, the acting general counsel of the Federal Mediation Service. "I've been involved in enough of these things to know that anytime one side accepts a federal mediator's proposal, there is always the possibility that somebody's going to make a charge like that," Moffett said. "Anytime you get a situation where one side accepts something in toto, there's bound to be a shot like that."

On Friday, the owners made a new proposal: they called it an amended version of the mediator's plan; Miller said it was the same as their old proposal with a "few numbers juggled."

The owners' proposal reduced to a maximum of 30 over three years the number of premium free agents that would require professional compensation; previously they had suggested a limit of 36 over three years. They eliminated the reentry draft for premium free agents, allowing them to negotiate with as many teams as they want. And they reduced, in some cases, the maximum compensation a team could receive for a premium free agent to the 22nd man on the roster. Previously, in many cases, a team would have received the 16th man on the roster as compensation.

Clark Griffith, a member of the board of directors of the owners' Player Relations Committee, said, "It's so fair, it's shocking."

The players rejected this proposal and offered to accept the mediator's plan -- in Miller's words, "bones, stubble and all" -- as their counter-offer.

While there is no doubt that a great gulf still remains, the numbers on the level of compensation have gotten closer. "There were some moves," said one source familiar with the negotiations, "but they are not in a settling mood."

By embracing the mediator's proposal, and aligning themselves with the neutral party's solution, the players accomplished two things: if there was any chance of the owners' accepting it, they had enhanced the possibility of a framework for a settlement; if not, they had succeeded in making the owners look bad.

As one source close to the players association put it, "I didn't suspect the owners would be in love with it. But if they were interested in a settlement, they could have said okay and bargained within that framework. They did neither. That tells me they don't want a settlement."

Four weeks ago, on the night the strike was called, one source close to the players association was asked what his scenario was for the end of the strike. He speculated that there would be a good chance for a settlement in a month and if that didn't work it would be a very long haul.

Asked if that was a fair assessment of the current situation, Miller said, "Probably."

Mark Belanger, player representative of the Baltimore Orioles, was more blunt: "Another month," he said.

With the All-Star Game postponed Friday and the owners' meeting Thursday a fait accompli, the major pressure points that could have forced some movement now are gone. The next pressure point will be the day the owners' $50 million strike insurance runs out, approximately a month from now.

"If we pass that," one source said, "the season's gone."