The National Bus and Rail Union is rejecting a call from the chief executive of Irish Rail to call off their forthcoming strike days.
A 48-hour strike has already caused the cancellation of trains last weekend.
Irish Rail's CEO David Franks wrote to both the NBRU and SIPTU requesting that stoppages on September 7, 8 and 21 are called off.
Dermot O'Leary of the National Bus and Rail Union said the request was untenable.
"The request from the chief executive David Franks to have discussions while keeping the pay cuts in place is just not tenable from our point of view," he said.