Horse breeder and trainer Jackie Dale MacLeod was thrilled when Rosecroft Raceway reopened last year after a two-year hiatus. That's because, during that time, MacLeod survived by racing and breeding horses out of state, even though his farm is based in Maryland.

With the Prince George's County executive backing National Harbor as the only acceptable site for a casino in the county, MacLeod and other horse owners and breeders say they fear for the track's future and their livelihood yet again.

"I roughed it through," MacLeod said of the two years when Rosecroft stopped live racing, filed for bankruptcy and then closed. "Now, it's a scary thing."

When Penn National Gaming bought Rosecroft last year for $11 million, it guaranteed racing only through 2012 and made it clear that it needed slots to ensure the survival of the struggling harness track.

But some racing officials and stakeholders say Penn National acquired Rosecroft knowing it had placed a long-shot wager to legalize slot-machine gambling at the site, which is not one of Maryland's five designated casino locations.

Penn National's warning was repeated at last week's hearing before a Senate committee considering a bill to expand the state's slots program. An executive for the national casino operator testified that slots at National Harbor on the Potomac riverfront would mean the demise of Rosecroft, a 124-acre property that some observers say has great redevelopment potential.

"We have a guarantee until the end of the year. But there's uncertainty in 2013," said Tom Cooke, president of Cloverleaf Standardbred Owners' Association. "Penn National was very clear and straightforward with us about their goals and ambitions. Should they make a decision to leave, no one would say, 'I'm surprised.' "

Penn National spokeswoman Karen Bailey declined to discuss Rosecroft's future, but did say that County Executive Rushern L. Baker III's support for a $1 billion Las Vegas-style casino had usurped the role of the state slots commission, which evaluates slots proposals and licenses operators.

"Our focus is to keep on the table the opportunity for Rosecroft to have slots or alternative gaming," she said.

Baker's administration does not agree that Rosecroft can't keep operating without slots.

County officials note that 7 percent of money generated by the state's casinos goes to horse racing purses. That money is divided, 80-20, between the thoroughbred and harness industries. An additional 2.5 percent goes to a fund for track capital projects.

"Current law provides a good number of support for the horse racing industry, which Rosecroft would continue to benefit from," said Brad Frome, Baker's deputy chief of staff. "Our perspective on this was what kind of facility would make most sense for the county. Having said that, we're very mindful of Rosecroft and its importance to the community."

The racetrack, which opened in 1949, has had a series of owners and a history of financial troubles.

Like many tracks across the country, Rosecroft has seen attendance and wagering erode as the sport's popularity declines. Maryland's racing industry also has faced growing competition from tracks in Delaware, West Virginia and Pennsylvania, which permit slot-machine gambling and table games such as blackjack.

In recent years, Rosecroft's fortunes have waxed and waned along with the chances of getting slots there. The property has long been eyed as a potential slots site because of its proximity to Washington.

The family of Peter G. Angelos, the Baltimore Orioles owner, pulled out of a deal to buy the track in 2005 when chances dimmed for legalizing gambling at tracks. Two years later, Penn National dropped its bid to buy Rosecroft when the track was not designated as a site for slot machines.

"Two steps forward. Three steps back," Cooke said of Rosecroft's troubled past.

Last year, Penn National bought the track in a bankruptcy auction, a process that attracted multiple bidders, including Angelos.

The bankruptcy trustee overseeing the sale sought bidders who would commit to resuming live racing at the track, said Michael J. Lichtenstein, the trustee's attorney.