ELMONT, N.Y. – Supporters and opponents of the raceday use of the diuretic furosemide will meet behind closed doors at Belmont Park on Tuesday in an attempt to resolve what has rapidly become racing’s fiercest debate. The Tuesday meeting is the first that will unite the two factions in a common setting since leading state regulators announced in March that they would seek to prohibit the raceday use of the drug, which is administered to approximately nine out of every 10 horses in the United States and Canada to treat bleeding in the lungs. The call for prohibition has been joined by several of the most influential groups in racing, including the Breeders’ Cup, the Jockey Club, the Association of Racing Commissioners International, and the Thoroughbred Owners and Breeders Association. The vast majority of trainers, however, remain staunchly opposed to any rollback in decades-old regulations that have provided for the raceday use of furosemide, which is commonly referred to by its trade name, Lasix. Given the entrenched positions, participants in the summit said this week that they doubted the two sides will be able to agree on a solution by the end of the day. Organizers of the conference have set a goal of merely advancing the discussion past its present stalemate. “We do not expect to come out with any specific agreement or major announcement,” said Alex Waldrop, the chief executive of the National Thoroughbred Racing Association, which is one of the three groups administering the summit. “This is the beginning of a conversation to find common ground. We don’t know what that is, or where the conversation will take us, but we hope this is where the discussion begins.” The Tuesday meeting will follow a series of related presentations on Monday, also at Belmont, that will focus on how regulators, trainers, and veterinarians in both domestic and foreign racing jurisdictions manage bleeding in horses, with or without furosemide. In addition to the NTRA, the two-day conference is organized by the Racing Medication and Testing Consortium and the American Association of Equine Practitioners. The NTRA and medication consortium receive funding from organizations representing both sides of the debate, while the equine practitioners, whose ranks are paid to administer raceday injections of furosemide, have long been in support of the use of the drug. The two sides have staked out familiar ground going into the summit. Supporters of a ban contend that furosemide use has eroded public confidence in the game and presented a barrier to developing new fans because of a perception that the drug enhances performance. In addition, supporters believe that furosemide use has increasingly isolated the United States and Canada from the rest of the racing world, where the raceday use of drugs is banned. By and large, horsemen contend that it is the rest of the world that is out of step by arguing that it is inhumane to allow horses to run without a drug that is considered to be effective in mitigating bleeding’s impact. Horsemen contend that furosemide does not enhance performance but instead allows horses to run to the best of their ability. The conflict between the two sides is decades old, but two developments over the past several years have rekindled the debate. On one side, longtime supporters of a ban have been emboldened by the industry’s decision three years ago to band together behind a rapid prohibition on the non-therapeutic use of anabolic steroids, a critical component of a larger movement to reform the sport’s medication practices. On the other side, horsemen point to a two-year-old study on bleeding conducted on horses racing in South Africa that concluded that the use of furosemide reduces both the frequency and severity of bleeding in horses. To North American horsemen, the study proved that furosemide was effective in treating a problem facing horses worldwide. “Most horses bleed,” said the trainer Graham Motion, who will speak during one of Monday’s panels. “I’m not so sure it’s a kind thing to let a horse go out there if you know it’s going to bleed and you know there’s a way to control it.” Although supporters of a ban acknowledge that furosemide can be effective, many argue that most horses do not bleed to an extent that the use of the drug is warranted. The South African study, for example, concluded that less than 2 percent of horses bleed severely. Claude R. “Shug” McGaughey, who trains for a leading proponent of a ban, the Jockey Club chairman, Ogden Mills “Dinny” Phipps, said the question facing the industry is whether racing can overcome the perception among the general public that furosemide is akin to performance-enhancing drugs that would be banned in other sports, such as blood-doping agents or stimulants. “I do know that out there the perception is not good,” McGaughey said. “I think whatever we do we have to work hard on getting that perception back to being good.”