The Philadelphia Stars, champions of the U.S. Football League, officially became the Baltimore Stars today, and owner Myles Tanenbaum announced that Edward DeBartolo Sr. had become a 50 percent partner in the team that will play its home games next season at Byrd Stadium in College Park.

Unlike two other USFL consolidations, this was not a merger between the Stars and the Pittsburgh Maulers, whom DeBartolo folded last week. The status of players under contract to the Maulers is uncertain. A few have guaranteed contracts, and the new partnership will assume those obligations.

The Stars will play their 1985 spring games in the University of Maryland's Byrd Stadium "and, in 1986 (when the USFL has said it will move to a fall schedule), we plan to make our home at Memorial Stadium" in Baltimore, Tanenbaum said. He will submit a proposal for a one-year, nonexclusive contract to use Memorial Stadium and expects no problems in reaching a lease agreement, although the team's reception here has been lukewarm, at best.

Carl Peterson, the Stars' president and general manager, said they also have an option to use Byrd Stadium in the spring of 1986 in case the league decides to play a split schedule that season. A decision on that is not likely to be made before the league completes a collective bargaining agreement with its players union, Peterson said.

In another development concerning the '86 season, network sources said NBC and ABC have told the USFL they were not interested in televising their games that year, the last of the current NFL contracts with the three major networks. CBS has not closed the door, but is not likely to make a deal for 1986, the same source said. He said he expects one or more of the networks to telecast USFL games in 1987, if the league survives.

Peterson said the Stars will pay less than the $100,000 rental fee reported Tuesday. Sources in College Park said the rental fee is based on a per game amount of about $9,000. By playing nine regular-season and two playoff games in Byrd Stadium, the rent would be $99,000. In addition, the Stars will purchase insurance and put money in escrow to cover damage to the grass playing field. The contracts have yet to be signed, a source at Maryland said.

The most significant development, though, was the joining of forces by Tanenbaum, a Philadelphia real estate developer, and DeBartolo, a Youngstown, Ohio, real estate developer and sports entrepreneur. The defunct Maulers' losses were estimated at between $5 million and $10 million last season. The Stars lost about $3 million, despite averaging 28,852 in attendance in Veterans Stadium.

The cost of fighting the NFL will become even more expensive, both on the field and off, with the switch to fall football in 1986 and the $1.2 billion antitrust suit the USFL recently filed against the NFL. Sources in pro football say USFL survivors of these battles will be owners with deep pockets and a willingness to spend that money.

"That was part and parcel of what we -- DeBartolo and I -- were looking at," Tanenbaum said.

"All you got to do is go back and look at Lamar Hunt, Sonny Werblin, Al Davis' group and Baron Hilton," Peterson said. "You've got to have the money and good management. But there are more guys with deep pockets in this league."

DeBartolo did not attend the press conference. Asked why DeBartolo was investing in the Stars after his bad experiences in Pittsburgh, Paul Martha, the former president of the Maulers who runs DeBartolo's franchises in the National Hockey League and the Major Indoor Soccer League, said, "He enjoys being involved in football. He doesn't give up easily."

Tanenbaum will remain managing general partner; Peterson will retain his titles as president and general manager and Jim Mora will continue as coach of a franchise that has won 35 of its 41 games in two seasons. Martha, who represents DeBartolo's interests, will oversee business matters and league business, Tanenbaum said.

Another notable absentee at today's press conference at the Baltimore Hyatt was Mayor William Donald Schaefer, who aggressively has pursued the return of the NFL's Indianapolis Colts or an NFL expansion franchise.

Tanenbaum and Schaefer met on the issue of a lease for Memorial Stadium for the first time this morning. Tanenbaum said he was proposing a one-year, non-exclusive lease. Pat Bernstein, Schaefer's press secretary, did attend the press conference and said Schaefer was attending the opening of another business.

"Walter Alston had a one-year contract with the Dodgers, and he managed them for 24 years," Tanenbaum said. "We plan to be here longer than 24 years."

A spokesman for Schaefer said the mayor "made it clear" to Tanenbaum that the city was going to continue trying to land an NFL franchise. The city has filed an eminent domain suit against the Colts, it has filed an amicus curiae brief supporting the NFL's bid for a review of the Raiders case by the U.S. Supreme Court and it is supporting legislation that would mandate Baltimore an expansion franchise.

"There's not a prayer they're going to get that team back, and it's four years away anyhow," Tanenbaum said. "I worry more about what I'm going to have for lunch today than that."

Peterson said the new partnership will assume the guaranteed contracts of "a small number" of Maulers players, including Heisman Trophy winner Mike Rozier, who was offered a chance to buy out the last two years of his contract. Of Rozier playing in Baltimore, Peterson said, "Anything is possible. But I'm not really excited about that. We already have a fine running back (Kelvin Bryant) . . . But I'd rather have him try out for our football team than sweep out shopping malls in Youngstown (DeBartolo's headquarters)."