The union is preparing to ballot its members on the government's response to its pay claim.
It follows a series of work stoppages in recent years.
President of the ASTI Ed Byrne says the row surrounds two main points of contention.
The union is preparing to ballot its members on the government's response to its pay claim.
It follows a series of work stoppages in recent years.
President of the ASTI Ed Byrne says the row surrounds two main points of contention.