SIPTU officials are due to hold talks with the company that runs the Dublin Port Tunnel today in an effort to avert a strike planned for the end of this month.
Workers at the tunnel have voted to strike from July 23 as part of a row over pay.
SIPTU, which represents the majority of the staff, says the workers are paid almost one third less than the normal rates in the sector.
If the strike goes ahead, it could close the tunnel and force hundreds of trucks back onto the streets of Dublin city centre.