The head of the LRC has said there is a lot of pent-up anger among workers at Dublin Bus and Bus Éireann.
While Kieran Mulvey is still hopeful agreement can be reached, he said there was a lot of work to do over the next two days.
Unions, management and staff at the Department of Transport are again meeting at the Labour Relations Commission in a bid to avert two further strike days this weekend.
Speaking on his way into talks, Kieran Mulvey said he did not know whether the strike could be called off.
"There's a lot of pent up anger and tension," he said. "It's complex and difficult, but the Commission is well used to being involved in these disputes and we remain hopeful that in the end of the day we can thrash out agreement between the parties."
Siptu says it wants to reach an agreement that "everyone could live with" in today's talks.
Drivers at Dublin Bus and Bus Éireann are preparing to down tools again this Friday and Saturday in a second round of strike action over plans to put 10 percent of routes operated by the two State-owned companies out to tender.