Tesco workers have warned they will place pickets outside stores as soon as the company changes their pay and conditions.
Around 1,000 long-term employees voted in favour of industrial action over the row on Friday.
Management has opened a voluntary redundancy scheme and deferred pay cuts for a month until May 16.
However, Brendan O’Hanlon from the Mandate trade union representing workers, says the delay will not stop them striking.
He said: "We now have served strike notice on the company and said to them that if they intend to make these changes without agreement with our union, we will immediately place pickets on the stores.
"Certainly in the first instance it will affect 89 stores, but then we plan to broaden it out as time develops."