Massachusetts is set to adopt tough new standards by the end of the year that would significantly reduce auto emissions linked to global warming, joining a growing list of states battling the auto industry to produce cleaner-burning cars.

Under rules proposed by the Romney administration, cars sold in the state after 2015 would have to emit 30 percent less carbon dioxide, 20 percent fewer toxic pollutants, and up to 20 percent fewer smog-causing pollutants than under federal standards, state officials said yesterday.

The regulations proposed by the Department of Environmental Protection mirror those enacted by California, which last year touched off a legal battle with automakers after it became the first state in the nation to target so-called greenhouse gas emissions from automobiles, officials said. After California adopted its standards, at least six Northeast states, as well as Oregon and Washington, moved to have the same limits, contending that as a bloc they could make a significant dent in gases that deplete the ozone layer. The rules are set to be phased in starting in 2009.