WASHINGTON (AP) -- Employers would have to correct injury-causing workplace conditions that require repetitive motion, overexertion or awkward posture under proposed regulations the Labor Department announced today.

``We are compelled to act. Employees are getting hurt. Workers are being sent home. People are suffering,'' said Charles N. Jeffress, assistant labor secretary for occupational safety and health.

The proposal would affect about 1.9 million work sites -- one of every three -- and more than 27 million workers. The department estimated the cost to employers at $4.2 billion a year.

Each year, 1.8 million workers have musculoskeletal injuries related to ergonomic factors and 600,000 people miss some work because of them, according to the Occupational Safety and Health Administration.

The injuries to muscles, nerves, ligaments and tendons include such problems as carpal tunnel syndrome, back pain and tendinitis.

``The fact is that work-related musculoskeletal disorders ... are the most prevalent, most expensive and most preventable workplace injuries in the country and it is time we do something about it,'' said Labor Secretary Alexis Herman.

The new rules would cover a broad range of workers from nurses aides who must lift heavy patients, to baggage handlers at airports and people who work at computers or on assembly lines.

Under the rules, a worker who has an ergonomic injury diagnosed by a doctor would be entitled to have the work environment fixed to relieve the cause -- by changing the height of an assembly line or computer keyboard, for example.

A worker who must be assigned to lighter duty during recovery from ergonomic injury would be guaranteed normal pay and benefits. A worker who must leave the job altogether would be guaranteed 90 percent pay and full benefits during recovery.

At workplaces with numerous incidents of ergonomic injury, employers would have to provide medical help and safety retraining for workers in addition to fixing physical problems.

In addition, the rule would require all manufacturers and companies with workers who do manual heavy lifting to provide preventive training.

The proposed rules, scheduled to be published in Tuesday's Federal Register, cannot become final until next year at the earliest, after a comment period that will include public hearings in Washington and other cities.

They have already been long delayed by opposition from business groups and some lawmakers who are concerned about the cost and have protested that there is not enough scientific evidence proving that ergonomic problems at work cause injury.

``There is a lack of consensus in the scientific and medical communities ... to justify a rule of this magnitude,'' said Jennifer Krese, director of employment policy for the National Association of Manufacturers.

Labor leaders applauded the government action, however.

``It confirms what workers have known for years -- that these injuries are caused by workplace hazards and can be prevented,'' said AFL-CIO President John Sweeney.

OSHA estimated that employers who need to correct problems will spend an average of $150 a year per work station fixed. The total cost was estimated at $4.2 billion a year.

The Labor Department estimates the new rules could prevent injury to about 300,000 workers annually and save employers $9 billion.

Ergonomic injuries currently cost $15 billion to $20 billion annually for workers' compensation and $30 billion to $40 billion in other expenses such as medical care, the agency said.