WASHINGTON — Senate Majority Leader George J. Mitchell came up with a new reason Thursday to take action against global warming.

In a Senate speech, Mitchell said that worldwide efforts to reduce emissions that may cause a warming of the planet would create thousands of new American jobs and reduce the nation’s trade deficit.

He made the speech before joining other senators in introducing legislation that would require the United States to stabilize emissions of carbon dioxide, the gas believed to cause global warming, at 1990 levels by the year 2000.

The U.S. Business and Industrial Council, a Washington-based research group, disputed Mitchell’s assessment. It claimed that international global warming curbs would result in an economic downturn totaling nearly 3 percent of the United States’ Gross Domestic Product, along with the loss of 700,000 American jobs.

The group warned that the imposition of expensive global warming curbs of the type advocated by Mitchell “could kill fledgling capitalist markets in Eastern Europe and the former Soviet republics.”

The debate over the economics of global warming came amid press reports that President George Bush has decided to attend an international summit in Brazil next month, where the industrialized nations are considering a treaty placing curbs on carbon dioxide emissions.

Mitchell said that Bush had cited economic arguments in seeking to avoid an international treaty on global warming. That is an “unfounded fear,” he said. Many scientific studies concur with Mitchell’s theory, but there also is strong evidence refuting models that project higher global temperatures.

According to Mitchell, environmental regulations curbing carbon dioxide would force American industry to increase its productive “efficiency.” That could result in a net increase of U.S. jobs, Mitchell said.

Mitchell based that projection on the worldwide leadership American companies hold in the development and manufacture of environmental equipment.

“The Organization for Economic Cooperation and Development estimates that worldwide about $200 billion annually is spent on environmental goods and services. The growth rate for this sector is projected to be about 5.5 percent per year according to that organization,” Mitchell said.

He said that a congressional study estimated that global environmental goods and services would grow to about $300 billion by the end of the decade.

“The United States share of this market,” Mitchell said, “is about 40 percent. … This is a potentially very lucrative market for America. This creates American jobs.”

Mitchell said that the United States should be taking an international leadership role in prodding other nations into increasing their environmental controls.