UNDATED (CNN) -- Walmart is fighting back against a planned walk-out by workers on one of the busiest shopping days of the year.
The United Food and Commercial Workers Union and its subsidiary OUR Walmart are calling for employees to skip work or walk off the job on "Black Friday", the day after Thanksgiving.
Walmart filed a complaint with a federal agency, accusing a labor union of illegally organizing picket lines and other demonstrations.
The planned walkouts build on a small strike at a Los Angeles Walmart in October that spread to 12 other cities.
A Walmart spokesman says the striking workers represent a very small minority of its more than one-million employees, and that the company is ready for the Black Friday shopping blitz.