A proposed compromise clean air plan between Midwestern states and Northeastern states has been rejected by parties on both sides, making it highly likely that the long-running dispute will be resolved only in court. Some of the Northeast states, which are forced to cope with pollution that blows in from power plants and other polluters in the Midwest and South, made the first effort at compromise last week, but it fell flat. Russell Harding, head of Michigan’s Department of Environmental Quality, said yesterday, “There won’t be any settlement because there isn’t any middle ground.” Last year, the EPA announced that it planned to impose a more strict national limit on nitrogen oxide emissions, the subject of this regional disagreement, but this spring a federal appeals court temporarily blocked the EPA from proceeding with that plan.