WASHINGTON (AP) -- The National Labor Relations Board has approved a new rule that requires private employers to display posters that tell workers about their right to form a union.

The rule requires businesses to prominently display the new posters that explain the right to bargain collectively, distribute union literature and engage in other union activities without reprisal.

Union advocates say the rule gives workers information they should know about their legal rights. But business groups, including the U.S. Chamber of Commerce, say the posters will make it appear the government is encouraging workers to join unions and will create a more favorable climate for union organizing.

The board said the rule, originally proposed in December, aims to help employees who may be unaware of their rights under federal labor laws. Another benefit will be promoting greater legal compliance by both employers and unions, the agency said.

Business groups have complained that the board, under the Obama administration, has taken a number of aggressive steps favorable to unions, which are trying to reverse years of membership declines. The board is poised to issue a much broader rule later this year that would allow votes to unionize workplaces to move more quickly, something unions have long sought.They are the first major rules the board has proposed in over 20 years.

Employers that post work rules electronically would have to put the union rights information on their websites as well as posters. The poster rule, which takes effect Nov. 14, exempts some small businesses based on various factors, including budget and payroll. Failure to post the notice could be considered an unfair labor practice.