The tram operator for Nottingham says further talks are planned to try to avert industrial action.
A spokesman for NET said further talks will be taking place with GMB early this week, beginning Monday, September 25.
“We are disappointed at the course of action taken by the GMB,” said Chris Wright, managing director of Nottingham Trams Limited.
Colin Whyatt, GMB organiser, added: “We’re urging tram bosses to step back from the brink and do everything in their power to save this year’s Goose Fair from travel chaos.
“Tram workers are facing the harshest cost of living crisis in a generation, with many of them unable to afford to live and shop in the city they work in.
“Time is rapidly running out, but our union is always open to negotiating a solution when tram bosses are ready to see sense.”
Nottingham City Transport (NCT) says it will continue to provide its regular bus services, but no extra replacement services are planned.
A spokesman said: “We expect to provide our usual levels of service throughout the Goose Fair period, but won’t have the capacity to provide dedicated tram replacement services.”