The Florida Hospital system and United Healthcare are embroiled in a contract standoff. If the two companies cannot agree on new terms by Aug. 15, about 170,000 United Healthcare customers in Central Florida would be unable to go to the 18 regional hospitals in the Florida Hospital network for nonemergencies or visit doctors employed by and facilities owned by the chain. Executives from both sides have been meeting since November, trying to negotiate a contract. But they remain at an impasse. At issue are the rates the insurer pays the hospitals for services. Florida Hospital officials say they want United Healthcare to pay the same rates as other major insurers. But a United Healthcare spokesman said Florida Hospital wants to raise rates 63 percent during a four-year period -- and calls that kind of hike "unreasonable."