When Ford Motor Co. Executive Chairman Bill Ford Jr. called the president last spring, he was hoping to defuse what was looking like a lengthy legal battle over the nation’s fuel-economy regulations for vehicles. The Trump administration wanted to significantly ease U.S. environmental rules. California had sued to stop that. The car industry was caught in the middle. Mr. Ford, calling from his Dearborn, Mich., office, urged the president to broker a compromise with California, according to people with knowledge of the conversation. …

President Trump was puzzled and told Mr. Ford his view was out of step with his industry peers. “He basically said: ‘You’re on your own’ ” to Mr. Ford, one of the people briefed on the call said. The call was part of a nearly yearlong push to fend off the expense and delays of competing fuel standards, but Ford miscalculated the White House’s appetite for a deal. Its efforts ultimately backfired, putting it at odds with the administration and other big car makers.

When Ford eventually made its own deal with California last summer, it drew an antitrust inquiry and spurred the administration to speed up efforts to strip California’s authority to set its own tailpipe standards. It also irritated Ford’s biggest rivals, including General Motors Co. and Toyota Motor Corp., which have since sided with the Trump administration on the issue.

The industry—more polarized than ever—is now facing a confrontation that could last for years, leaving it in a costly limbo. The Trump administration in the coming weeks is expected to finalize new fuel-economy rules that significantly dial back the targets adopted under President Obama. Mr. Trump’s legal fight with California, the state that is the U.S. auto industry’s biggest market, is expected to be bitter and drawn-out.