ROMULUS, Mich. -- Standing in the heart of car country on the eve of the 30th anniversary of Earth Day, Vice President Al Gore wholeheartedly embraced one of his most controversial environmental stands and pushed it one step further Friday, asserting the internal combustion engine could be eliminated before the year 2017.

In his 1992 book "Earth in the Balance," Gore described the internal combustion engine, used on most cars and trucks, as an outdated technology that is one of the main sources of carbon dioxide production and thus poses a "mortal threat" to society. Gore and other environmentalists argue that the release of carbon dioxide into the atmosphere has created a hole in the ozone layer which they in turn cite as the principal cause of global warming.Gore told a group of truck manufacturers and labor leaders here of the "fierce criticism" he received for such comments: "I expected that criticism then and I wear it as a badge of honor today."

In announcing a new government-corporate partnership aimed at developing more fuel efficient trucks, Gore pitched his general belief that environmental protection can enhance the economy. "If we make the right investments, if we make the responsible choices then we do not have to choose between the economy and the environment," he said. The vice president's speech Friday, delivered in a truck depot outside Detroit, was his most forceful address on the environment of the 2000 campaign. Although he made his name in politics as an ardent environmentalist, his political advisers have split over the wisdom in running for president on the issue, wih some concerned that his stridency has alienated the business community. Others, citing pollution problems in Texas, say the environment is a weakness of Gov. George W. Bush's worth exploiting.

Set against that backdrop, Gore's comments Friday were all the more striking. "We have heard, and in the months ahead I am sure we will hear, every possible scare tactic on this issue," he said. "But we will not give in and we will not back down. It is not extreme but mainstream to champion cleaner fuels and energy efficiency."

As part of the Earth Day celebrations, Gore has reissued "Earth in the Balance," with an aggressive new foreword maintaining his earlier commitment to tough environmental protections. And in his speech Friday, Gore was hardly modest in describing the political risks he has taken in the name of clean air and water.

"More than a decade ago when I set out to write "Earth in the Balance," I was warned not to do it; that it was politically foolish to make so clear a commitment to environmental protection written down in black and white for all to see," he said. "But for me, a commitment to the environment has always run deeper than politics."