The RMT union will ballot staff for strike action which could potentially cause ‘severe disruption.’
The dispute is over safety and working conditions.
The union claims there are safety issues at stake due to an increase in workload and union members being pressured to maintain timetables, even with ongoing maintenance issues over trains.
The RMT says it has raised concerns about this for more than a year.
The RMT represents train managers, engineering and maintenance workers, and terminal control centre workers.
Depending on the ballot outcome, possible strike dates could be announced next month.
Further talks between the RMT and Eurostar management are being held this week.
The union has to inform Eurostar of strike dates two weeks in advance which could affect the pre Christmas period.