Unions and management at Irish Rail are locked in talks this afternoon.
Workers are looking for an almost 4% hike in their wages.
SIPTU and the NBRU said today's negotiations at the Workplace Relations Commission are make or break.
SIPTU's Paul Cullen said his members may consider strike action if there is not an offer made today.
"Unless a pay offer is on the table today - it's the last opportunity to deal with that - we will then seek a mandate from our membership in relation to either industrial action or strike action," he said.
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