Talks at the Labour Relations Commission between management and unions at Dublin Bus and Bus Éireann aimed at averting industrial action have adjourned until tomorrow.
Both sides have said they are keen to find a resolution to the dispute, ahead of a two-day strike which is due to begin on Friday.
Yesterday both sides met for two hours and returned this morning for what was described as 48 hours of intensive negotiations.
Following yesterday's talks, SIPTU's Owen Reidy said there was nothing new on the table since the last time the sides met at the LRC except time.
National Bus and Rail Union general secretary Dermot O'Leary said the issues had become more crystalised and all sides now understood the others' position.
He said his union would work as hard and as long as it takes to resolve the dispute.
The talks are aimed at averting industrial action this weekend in the dispute over plans to put 10% of bus routes out to tender.
All services at the State-run bus companies were halted on 1 and 2 May.
SIPTU and the NBRU plan further action this Friday and Saturday, 15 and 16 May, as well as three days of action on 29, 30 and 31 May.
A previous attempt by the commission to resolve the row ten days ago failed to prevent the bank holiday stoppage, and there has been no sign that positions have softened.