WASHINGTON — More than 4 million U.S. workers will become newly eligible for overtime pay under rules to be issued today by the Obama administration.

The policy changes are intended to counter erosion in overtime protections, which date from the 1930s and require employers to pay 1½ times a worker’s regular salary for any work past 40 hours a week.

In the fast food and retail industries in particular, many employees are deemed “managers,” work long hours, but are barely paid more than the people they supervise.

Under the new rules, first released in draft form last summer, the annual salary threshold at which companies can deny overtime pay will be doubled from $23,660 to nearly $47,500. That would make 4.2 million more salaried workers eligible for overtime pay. Hourly workers would continue to be mostly guaranteed overtime.

The White House estimates that the rule change will raise pay by $1.2 billion a year over the next decade. In addition, some companies may instead choose to reduce their employees’ hours to avoid paying the extra wages.

“Either way, the worker wins,” said Vice President Joe Biden on a conference call with reporters Tuesday afternoon.

Business groups, however, said the changes will increase paperwork and scheduling burdens for small companies and force many businesses to convert salaried workers to hourly ones to more closely track working time. Many employees will see that as a step down, they said.

“With the stroke of a pen, the Labor Department is demoting millions of workers,” said David French, a senior vice president for the National Retail Federation. “Most of the people impacted by this change will not see any additional pay.”

The overtime threshold was last updated in 2004 and now covers just 7 percent of full-time, salaried workers, administration officials said. That’s down from 62 percent in 1975.

The higher threshold, which will take effect Dec. 1, will lift that ratio back to 35 percent, Labor Secretary Tom Perez said.

The new rule is intended to boost earnings for middle- and lower-income workers, Perez said, which have been stagnant since the late 1990s.

Overtime pay hasn’t gotten as much attention as nationwide efforts to increase the minimum wage, but it could have a broad impact.

“This in essence is a minimum-wage increase for the middle class,” said Judy Conti, federal advocacy coordinator for the National Employment Law Project, an advocacy group.

Overtime has become a sore point for many managers, assistant managers, and management trainees in the fast food and retail industries.

Despite their titles, they have complained in lawsuits against chains such as Chipotle and Dollar General that they spend the vast majority of 50- or 60-hour weeks working cash registers, mopping floors, or performing other tasks typical of regular employees. Yet they don’t get paid time and a half when they clock more than 40 hours in a week.