President Bush and Canadian Prime Minister Brian Mulroney said Sunday their nations would begin negotiations on an air pollution agreement this month. The announcement was foreseen a year ago when Bush decided to seek new controls on the sources of acid rain, an issue Canada has been complaining about for a decade. Both houses of Congress have passed different versions of legislation requiring utility smokestacks to reduce extensively emissions of sulfur dioxide and nitrogen oxides, the principal raw materials causing acid rain. Environmentalists monitoring the economic summit welcomed the announcement and said it was inevitable. In a session before the summit officially begins Monday, Bush and Mulroney set an informal timetable for talks to begin on an air pollution agreement. William Reilly, administrator of the Environmental Protection Agency, will meet with his counterpart, Robert de Cotret, in Ottawa, Canada, on July 16, the leaders said. Formal negotiations should begin shortly after that, they said. ``I think this day will be long remembered in the history of our relationship for the significant departure it constitutes from past positions,'' Mulroney said. He and other Canadian leaders have been rebuffed in the past in their attempt to prod the United States into curbing pollutants. A White House announcement said the talks with Canada would cover monitoring of emissions, exchange of information and settlement of disputes. Scientists on both sides of the border agree about half the acid rain falling in eastern Canada originates from emissions generated by utilities and smokestacks in the United States. Because of wind patterns, about a quarter of the acid rain falling in the Adirondack Mountains of New York States originates in Canada. Former President Reagan argued that not enough was known to conclude that acid rain was a serious problem; Canada said marine life in as many as 14,000 lakes is in jeopardy. Environmentalists, meanwhile, denounced what they said was the failure of the seven summit nations to live up to the rhetoric of last year's meeting in Paris in which they pledged to protect the world's environment. The leaders agreed in 1989 to end production of chemicals that destroy the earth's protective ozone layer, said George T. Frampton, president of The Wilderness Society. ``The reality is that our forests are being cut just as fast as they were a year ago, Frampton said. ``Carbon dioxide and other greenhouse gases are being emitted into the atmosphere at just the same high volume, or even greater, than that of a year ago. Population growth and ocean pollution have continued unabated.'' An environmental coalition of 150 groups is keeping a scorecard designed to hold governments accountable by publicizing their records, Frampton said. The environmentalists have already ranked the countries attending the summit. West Germany was rated top, followed by France, Britain, Canada, the United States, Japan and Italy. The countries were ranked based on their policies on conserving energy and reducing the threat of global warming; protecting biological diversity such as that found in tropical forests, abating pollution of the oceans, controlling population growth, helping the cleanup of Eastern Europe and helping develoing nations. Germany's high score was ``the best of a bad lot,'' said Jay Hair, executive vice president of the National Wildlife Federation.