SOUTH LAKE TAHOE — California is close to bringing two more automakers into its plan to reduce tailpipe emissions below national targets, Gov. Gavin Newsom said Tuesday, despite what he called the Trump administration’s “pathetic” attempts to pressure the industry not to get involved.

Newsom said Mercedes-Benz and another company are talking to state officials about joining a voluntary compact, announced last month, to raise the fuel efficiency of their cars and light trucks to about 50 miles per gallon by model year 2026. The governor declined to identify the second company.

The New York Times reported Tuesday that after California unveiled an agreement in July with Ford, Honda, BMW and Volkswagen, a senior Trump adviser summoned three other car manufacturers to the White House to urge them to stick with the president’s proposal to weaken plans to raise national auto emissions standards.

Newsom called it “shameful” that the administration “threatened” companies and told them how they should do business.

“That’s stuff you read in crackpot third-world countries, not in the United States of America. This is pathetic,” Newsom said following a speech at an annual environmental summit at Lake Tahoe. “And it shows the weakness of the administration, the weakness and effeteness of their call to roll back this effort.”

In addition to Mercedes-Benz, one of the three companies that participated in the White House meeting — Toyota, Fiat Chrysler and General Motors — is also considering bucking the Trump administration, according to the Times. Newsom said he wouldn’t name the other company because “I don’t want to get in trouble.”

“It’s a constant, never-ending effort to try to bring these other car companies in,” he said.

California is negotiating with automakers as it remains embroiled in litigation with the administration over President Trump’s push to undo fuel-efficiency rules established under former President Barack Obama. If Trump succeeds, national fuel economy standards would continue to increase to roughly 37 miles per gallon in 2020, then stop there, well short of the currently planned 47 mpg in 2025.

The auto industry initially sought relief from the Obama targets when Trump was elected. But it has become concerned that the national automobile market could be cleaved in two if California, where more cars are sold than in any other state, and its allies continue to pursue stricter emissions targets than the federal government.

The U.S. Environmental Protection Agency wants to repeal a waiver that has allowed California and 13 other states to set tougher standards for tailpipe emissions than the rest of the country. The administration says its move to roll back fuel-efficiency goals is intended in part to make cars more affordable. When California unveiled its arrangement with automakers in July, an EPA spokesman dismissed it as “a PR stunt.”

Under the agreement, the four participating companies — which account for about 30% of U.S. car sales — will have to reduce greenhouse gas emissions from their cars by almost 4% annually for five years. About a quarter of that mandate could be offset by credits for adopting cleaner technologies in the vehicle design, such as improved internal temperature controls, and by selling more electric or hybrid cars.

“This was a big blow to the Trump administration that we were able to accomplish, and I don’t think they saw it coming,” Newsom said Tuesday. “This idea that they’re helping the automobile manufacturers, that’s now just blown up. It’s a complete myth. It was made up.”

He said the willingness of more carmakers to get on board with California’s plan showed that Trump was not responding to the desires of the auto indsutry and was instead trying to help oil companies earn bigger profits.

“And that’s pretty remarkable, that he’s willing to sacrifice the air and clean water, the health of this country and its competitiveness for short-term gains,” Newsom said.

Alexei Koseff is a San Francisco Chronicle staff writer. Email: alexei.koseff@sfchronicle.com Twitter: @akoseff