The New York Yankees became the first major league baseball team to sell all of its television rights to a cable network Friday when they announced a 12-year deal with the Madison Square Garden Network.

The MSG Network will show 75 games in each of the 1989 and 1990 seasons. WPIX-TV, which has carried Yankees games for 38 years, will broadcast 75 games each of those two years under an existing contract. Beginning in 1991 and through the 2000 season, MSG has exclusive rights to 150 games a season.The value of the package was not announced, but a source familiar with the deal said it was worth about $500 million.

Under the contract, MSG could resell its rights to an over-the-air channel. Bob Gutkowski, president of the MSG Network, said he did not know if any games would be resold. If they are, "WPIX has the first option to license such rights," according to Paul Schneider, an MSG spokesman.

Marty Appel, a spokesman for WPIX, said the station intended to try to buy rights to over-the-air games from MSG. But he said no deal was in place.

"It's a long way off, it's a hard to look ahead from 1988 to 1991," he said. "MSG says there's a lot of time."