After a night of hope that a new proposal by federal mediator Kenneth E. Moffett might offer a basis for a settlement in the 30-day-old baseball strike, talks broke off shortly after 2 a.m. without an agreement.

After the negotiations broke off, Marvin Miller, executive director of the Major League Baseball Players Association, said the players had offered to accept in total Moffett's plan.

However, representatives for the 26 major league owners said they could not accept the proposal as written and, instead, offered one of their own. Lee MacPhail, American League president, said, "There are certain portions that owners have very serious problems with. We'd like very much to accept but we can't."

The owners' chief objections to Moffett's proposal were the level of compensaiton he suggested for free agents and to the fact that only players moving from a weak team to a stronger one would require what they consider adequate compensation.

The negotiations were to resume today at 11 a.m.

Before the talks broke off this morning, representatives of the owners and players met for five hours Friday and continued talking until 2 a.m.. In between sessions Friday, Baltimore's Doug DeCinces, the American League representative, said, "We discussed the pluses and the minuses. Both sides have some objections, some problems. But we feel it has the possibility of a skeleton of a successful agreement."

Earlier Friday, Baseball Commissioner Bowie Kuhn announced that the All-Star game, scheduled for Clevend Tuesday, had been postponed. It will be rescheduled for a later date, he said.

Commenting on Moffett's proposal early Friday, Minnesota's Clark Griffith, a member of the board of directors of the Player Relations Committee, said, "I think it should be considered in the light in which it was intended . . . I don't think it was intended as a settlement proposal. It was to try to get people to talk to each other."

While there was little doubt that Moffett's proposal offered the best hope for a settlement to date, one source close to the negotiations cautined against undue optimism that a settlement was imminent. "It's going to be perceived as encouraging," the source said. "But they are not close enough yet."

Still, others close to the talks said that the plant might be successful and indicated that if this proposal does not produce a settlement soon, the strike could go another month.

The proposal was delivered to Ray Grebey, the owners' chief negotiator, and Miller Thursday. The plan contains elements from previous proposals made by both sides regarding free-agent compensation, the issue that prompted the strike. It does not include the players' concept for pooled compensation. However, the form of direct compensation included in the mediator's plan is much less than the owners had previously suggested, allowing a team to claim at most the 25th man on the roster of the team signing a free agent. Previously, the owners wanted the 16th man on the roster.

In addition, Moffett proposed:

Placing a maximum of 12 a year on the number of premium free agents requiring compensation in the form of a professional player (the owners last week proposed such a maximum but included a carryover provision on their plan).

Defining premium players as those in the top 20 percent at each position. Those players would be ranked on the basis of performance statistics compiled over a two-year period. The performance statistics would be those proposed by the owners on May 19.

Once the players werer ranked, only the top 12 would be subject to compensation in the form of another professional player. The rest of the players in the top 20 percent would require a special pick in the amateur draft as compensation.

Premium players, the top 20 percent, would not be subject to the re-entry draft and would be able to negotiate with any number of clubs. At present , a free agent may be selected by only 13 clubs in the re-entry draft.

Any player who had previously been a free agent, or had more than 12 years' major league service, or who was older than 35 at the time he declared free agency, would not be a premium player. These players, and the remaining 80 percent not defined as premium, would be subject to the same rules on free-agency that now exist.

The most significant departure in Moffett's proposal comes in the level of compensation, which his proposal would adjust according to the won-lost records of the teams signing and losing the free agent.

Moffett proposed dividing teams into three categories: (A) the top nine in won-lost record over the previous two years, (B) the middle eight teams and (C) the bottom line.

Under his proposal, if a team that signs a free agent has a better record than the team losing the free agent, the signing team must give up a player as compensation. A team that signs a free agent and has a poorer record than the team losing him would not have to provide compensation.

In other words, if Yankee pitcher Ron Guidry, who is scheduled to become a free agent at the end of this season, wanted to sign with the San Diego Padres, the Yankees would get no compensation. If, however, last year, the Padres' Dave Winfield wanted to sign with the Yankees (which, of course, he did), the Padres could have taken the 25th man on the Yankee roster as compensation.

If a player from the New York Mets, a C team over the last two years, signed with the Yankees, an A team, the Yankees would be able to protect any 24 players in their system. The Mets would be able to pick any of the Yankees' unprotected players as compensation.

If a free agent from a B team signs with an A team, or if a free agent from a C team signs with a B team, then the team signing the free agent would be allowed to protect 30 men in its system. The team losing the free agent would then be allowed to select any of the unprotected players.

In the event that a free agent from a B team signs with another B team, or any other lateral move, compensation would be strictly an amateur draft pick.

By adjusting the level of compensation according to the rank of the teams signing and losing players, the proposal addresses the owners' concern about competitive balance. By reducing the level of compensation to the bottom of the 25-man roster or below, the proposal address the players' concern about the drag on mobility and bargaining power.

To further diminish the players' concern that direct compensation would discourage teams from bidding on free agents, Moffett also proposed that the team losing the free agent and providing compensation in the form of a professional player would have to pay for it.

One of the players' arguments against direct compensation is that if a team had to lose one of its own players ot sign a free agent, it would be reluctant to spend the money it had to in order to sign the free agent. So, Moffett proposed that the team losing the free agent pay the team signing him $200,000 or $150,000 depending on whether the team lost its 25th man or its 30th man. The payment seems geared to providing an inducement to the team signing the free agent to pay as much for his services as it can.

Referring to the proposal, a source on the players' side said, "There are things in it that assuage the players' concern over direct compensation. If the owners are interesed, we'll be here all right."

Although Moffett made his proposal available to Grebey and Miller Thursday, it was not discussed, except in the most general terms, at the owners' meeting Thursday night. Grebey told the owners that he was unable to discuss it because it was confidential. Sources say, however, there was no agreement that the negotiators could not discuss the proposal with their principals, and that, in fact, Moffett had hoped Grebey would do so.

Fehr said, "Marvin certainly felt free to discuss it with anyone on our side. I find it incredible that Grebey felt he had to keep it secret from his own people."