Strike action at Bus Éireann and Dublin Bus next month could cost the companies up to €5 million.
Bus Éireann says it's a huge loss and wants more talks to try and hammer out a solution.
The NBRU and SIPTU yesterday announced a combined total of 7 days industrial action in May, over proposals to privatise some routes on the network.
General Secretary of the National Bus and Railworkers Union Dermot O'Leary wants action from the Minister for Transport, after Paschal Donohoe yesterday called for the strike to be called off.
