The Prince George's County government is preparing to spend about $1 million to buy the dilapidated Marlboro Race Track, which figured in the political corruption trial of former Maryland governor Marvin Mandel.

The track, on 150 acres near the county set of Upper Marlboro, has been closed since 1973. It is now used as a parking lot for county government employes.

County Executive Lawrence J. Hogan refused yesterday to "confirm, affirm or deny" that purchase negotiations are going on or that agreement has been reached, emphasizing that any such deal would require both his approval and that of the County Council. Sources said only small details of a purchase agreement -- such as a settlement date -- remain to be worked out.

Hogan did say he thinks the county should buy the property soon "while the land's still cheap. The idea is to buy the land and hold it for posterity." In the meantime, it can continue to serve as a county parking lot, he said.

Negotiators for the county and Gibraltar Pari Mutuel Inc., the New Jersey-based holding company that owns both the Marlboro track and the Bowie Race Course, apparently have been working on a deal for several months.

Alvin Karwacki, general manager of the Bowie track, and a vice president of Gibraltar, said earlier this week that the sale price would be about $1 million but emphasized no final agreement had been reached.

Although the Marlboro track is now a crumbling and isolated landmark for travelers along Maryland Rte. 4, years ago it was the pride of the county, a posh gathering place with record numbers of bets placed and visitors attending.

By 1970 it began losing its following to bigger tracks, such as Bowie's milelong course. A year later, Marlboro Associates, a partnership that secretly included friends of Mandel bought the track. Mandel then used his influence to get the 1972 General Assembly to give it more racing dates, which increased the track's value.

Shortly thereafter, the associates sold the track at a healthly profit. When Gibraltar took it over, it transferred its racing dates to Bowie, where the number of bettors and horses is greater.

Earlier this month, the U.S. Supreme Court refused to review the political corruption convictions of Mandel and five of his former associates; the former governor and four of the five are expected to start serving prison sentences next month.

Prince George's officials have been interested in buying the property for years. In 1975, the Board of Education persuaded then-county executive Winfield Kelly to buy the track from Gibraltar and use the land for new school administration buildings, according to one former top Kelly aide.

Just as Kelly agreed to begin negotiations, the first newspaper reports of the Mandel deal began to surface and Kelly dropped the idea -- "like a hot potato," in the words of the aide -- apparently fearing possible political taint. Both Kelly and Mandel are Democrats. Hogan said yesterday, "I don't have to worry about buying it like Kelly had to. I'm a Republican and no one would think I was tied into the Mandel scheme."