The Trump administration released its far-reaching rollback of Obama-era tailpipe pollution standards Tuesday, describing the new looser rules as reflecting its "largest deregulatory initiative" yet.

Instead of improving fuel efficiency by about 5% a year over five years, the new standards require a 1.5% annual improvement, which will result in sharp increases in greenhouse gas emissions.

An earlier draft of the rollback envisioned freezing the standards, requiring no improvement in fuel-efficiency in those years. But following broad pushback, including from environmental experts as well as some carmakers, administration officials said they opted to require modest gains in efficiency.

James Owens, acting administrator of the National Highway Traffic Safety Administration, which spearheaded the rulemaking effort, said the final proposal was changed to incorporate more than 750,000 public comments.

Academic experts and advisers to the federal government had called the administration's analysis into question, pointing to a series of errors and faulty assumptions.

Owens said "significant changes were made to the analysis" after considering "hundreds of highly technical comments."

Administration officials asserted that the rule would lead to 3,300 fewer traffic fatalities over the lives of the cars built with the new standards, arguing that more people would get into newer, safer cars because they would be more affordable. An earlier draft had projected the weaker rules could save 12,700 lives over the coming decades, but the assumptions in those calculations were widely assailed.

The claimed potential for lower traffic deaths under the new rules also does not account for increases in deaths due to illnesses from greater pollution. An official from the Environmental Protection Agency asserted Tuesday such estimates from outside groups have been overstated.

"Today, President [Donald] Trump is keeping his promise to autoworkers made three years ago that he would reinvigorate American auto manufacturing by updating costly, increasingly unachievable fuel economy and vehicle CO2 emissions standards," Transportation Secretary Elaine Chao said in a statement.

But Rep. Debbie Dingell, D-Mich., who represents a district with a heavy auto industry presence, said the rules will cause "serious and detrimental harm to an industry that needs certainty."

"The Administration's inability to work with all stakeholders to develop a consensus proposal will cause more uncertainty and chaos for an industry recently turned on its head by the COVID-19 epidemic," Dingell said, adding that more litigation is sure to follow.

Officials in California, which sets higher fuel efficiency standards shared by many other states, said the new rules would not accomplish what the administration claims they will.

In a statement from the office of Attorney General Xavier Becerra, who has helped lead legal challenges to the administration rollback, California officials said the rule will "fail to increase fuel economy." That's because the industry is already making improvements "on their own at 2% without the rule," the statement said.

They also wrote that the rule "will not save lives" and "is a wash at best. Increased air pollution will likely take more lives than the plan purports to save."

Becerra said the rules violate federal law and the state is prepared to take legal action on the rule.