General Motors Corp. chairman Roger Smith believes the imposition of a 15 cent per gallon tax on gasoline would mean the loss of 100,000 jobs in the U.S. auto industry.

General Motors is the only one of the top three U.S. carmakers that opposes increasing the federal gasoline tax to help cut the nation's deficit.Smith said he could support raising the gasoline tax to pay for highway improvements, but opposed using it to reduce the deficit.

Both Ford Motor Co. and Chrysler Corp. are in favor of using the tax, currently at 9.1 cents a gallon, to reduce the deficit if the money is specifically earmarked for that purpose. U.S. oil industry analysts estimate that each 1 cent increase in the tax would generate about $1 billion in additional revenues.

However, Smith said the auto industry would suffer if the tax were raised. "The fuel tax is a cruel tax," he said, adding that a rise could adversely affect car sales in 1989. "That could spell trouble for our industry," he added.

By contrast, Chrysler chairman Lee Iacocca said the country needed such a tax increase.

In a letter to the editor of the New York Times, Iacocca said he had been calling for a 50 cent per gallon federal gasoline tax since the energy crisis of 1979.