DHL Express will cut 320 jobs in Ireland and close a number of depots after a downturn in its domestic delivery business.
The company said it wanted to focus on its international delivery service and the cutbacks would mean a slimmed-down delivery service here in Ireland.
The company wants to make the job cuts by August.
Sitpu organiser Pat Ward said the union was willing to do its utmost during the days ahead to work with management in an effort to save as many jobs as possible.