The casino is terminating its employees' pension plan in favor of other payment options.
The dispute is rapidly shaping up as a test of wills between the Carl Icahn-owned casino and the powerful union, which brought the resort to its knees with a 2004 strike.
Local 54 of the Unite-HERE casino union is asking groups that have booked events at the Tropicana to take their business elsewhere.
The union has used the tactic of persuading large groups to avoid a particular casino before. Last summer, during a contract dispute with Resorts Casino Hotel, it persuaded at least three convention groups to cancel, and also held many noisy protests at Resorts.
