Senate leaders and President Bush compromised Thursday on future air pollution controls for automobiles, factories and electric power plants, enhancing chances that a clean air bill will pass this year. The agreement, after more than three weeks of closed-door negotiations, was viewed as a middle ground likely to attract enough support to thwart continuing regional opposition in the looming Senate debate. Majority Leader George Mitchell, D-Maine, called the compromise a ``sound and comprehensive'' agreement that will substantially improve air quality over the next decade. He planned to bring the legislation to the Senate floor on Monday. ``President Bush is extraordinarily pleased with the agreement. It is a milestone, an enormous step forward,'' said Roger Porter, the president's chief domestic policy adviser. Porter said the administration would attempt to expedite Senate passage and seek a similar agreement in the House, where clean-air legislation remains in committee. But the compromise is still likely to encounter stiff industry lobbying, largely because of its estimated $20 billion to $40 billion annual cost to the economy. Both industrial and environmental groups issued statements Thursday denouncing the compromise. Some senators also have expressed concern that the bargaining weakened provisions in the original Senate bill that would have required stronger automobile emission controls to combat urban smog. Other have voiced continued concern about the impact of acid rain controls. ``The agreement fails to require the controls we need to provide clean air in the nation and in New Jersey,'' said Sen. Frank Lautenberg, D-N.J., who participated in some of the private discussions, but said he would not support the compromise on the Senate floor. Sen. Bob Dole, R-Kan., the minority leader, called the compromise ``a giant step forward'' in revising federal air pollution laws for the first time in 13 years. But he cautioned that many senators likely will seek changes when the measure goes to the Senate floor. He urged Mitchell ``not to handcuff anyone'' during the floor action by rushing to cut off debate. The agreement made some accommodations to regional interests, especially those concerned about the local economic cost of acid rain controls. On that score, the compromise continues to require a 10 million ton annual reduction of sulfur dioxide emissions, but allows Midwest utilities to achieve extra credits and allowances that could be sold to other utilities to recoup some of the costs. Plants that use new technology _ instead of switching away from high-sulfur coal to another fuel _ could delay compliance for two years would receive additional credits for early cuts in emissions, provisions designed to help West Virginia's coal industry. About a dozen senators from the Midwest had threatened to filibuster the legislation if some accommodation were not met to ease their concerns about the high costs of the pollution controls. Mitchell said he still could not discount the threat of a filibuster, but various Senate sources suggested that with the compromise, Mitchell likely would have enough votes to halt debate. Sen. Robert Byrd, D-W.Va., said he would seek additional changes to the bill. But ``I'm not going to engage in any filibuster,'' he said. ``We did not have a choice between the good, the bad and the ugly. We had a choice between ugly, uglier and ugliest,'' said Sen. Christopher Bond, R-Mo., who during the private talks sought to work out provisions to ease the plight of Midwest utilities that rely heavily on high-sulfur coal. The breakthrough on the legislation came Wednesday when leaders agreed on pollution curbs on automobiles. The compromise eliminates an automatic second round of auto tailpipe controls, although such measures could be put into effect if more than 11 of 27 cities with ``serious'' ozone pollution problems fail to meet federal air quality standards at the end of this decade. The White House had strongly opposed the second round of controls, as had the auto industry. But environmentalists, state pollution control officials in areas with the dirtiest air, and some senators argued the second round of controls are needed to deal with smog in such areas as southern California and the Northeast. In the final days of negotiations, an agreement also came on the acid rain provision, after senators from the West were assured that the utility emission controls would allow for future growth in electric capacity and some accommodation was made to the Midwest region. Earlier tentative agreements were struck on how to curb toxic and smog-causing emissions from industrial plants. Under the compromise, industrial plants will have to use the best available technology to curb releases of 192 toxic chemicals including carcinogens, or cancer-causing agents. Early in the next decade a ``health standard'' would require plants to reduce emissions further, if the cancer risk to nearby residents is still too high. A broad range of industries and businesses also would have to comply with tougher controls on smog-causing emissions. The compromise, however, would exempt thousands of smaller polluters, which would have been covered by the original Senate bill. Environmental groups, meanwhile, chastised the negotiations and said the compromise agreement severely weakened the original Senate bill. ``The back-room dealing has generated bad deals for the American people,'' complained Richard Ayres, chairman of the National Clean Air Coalition. But industry did not like the agreement either. The Edison Electric Institute called the agreement ``unnecessarily costly'' for the nation's utilities. The Chemical Manufacturers Association called the tougher controls on toxic chemicals too stringent and politically motivated and ignoring scientific facts about health risks. The agreement is ``far from what business and industry would consider acceptable,'' said William Fay, administrator of the Clean Air Working Group, industry's umbrella lobbying organization on clean air issues. ``There's no question the bill has been improved but there are still some real problems,'' said Helen Petrauskas, vice president for environmental engineering at Ford Motor Co. Though the bill avoids any requirement that automakers sell a specific number of cars that burn clean fuels, which favors industry, the exhaust standards are still tougher than the industry would like, she said.