Wal-Mart Stores Inc. (WMT), the world's biggest retailer, said Thursday it is extending its $4 generic prescription drug plan to another 12 states, bringing to total to 27 states.

The move brings 1,008 more stores under the program, under which Wal-Mart charges $4 for a one-month supply of 314 different prescriptions. That number includes 143 drugs in a variety of dosages and solid or liquid forms.

Bentonville, Ark.-based Wal-Mart rolled out the program in Florida three weeks ago and last week added 14 states to the list. The low-priced drugs are now available in 2,507 Wal-Mart, Sam's Club and Neighborhood Market stores.

The company said in a news release that it accelerated the launch of the low-priced prescriptions because of customer demand.

Analysts say the program will help Wal-Mart by bringing in more customers who will shop in other store departments, and extend its reach in another segment of the retailing industry - the drug store business.

Union-backed Wal-Mart critics have also accused the company of using the low-priced drugs to divert attention from its own employee health insurance plan, which anti-Wal-Mart groups say does not offer adequate coverage.

States added Thursday were: Alabama, Georgia, Iowa, Kansas, Maryland, Michigan, Mississippi, Missouri, New Hampshire, Ohio, South Dakota and Virginia.

States already with the program were: Alaska, Arkansas, Arizona, Delaware, Florida, Illinois, Indiana, Nevada, New Jersey, New Mexico, New York, North Carolina, Oregon, Texas and Vermont.