SIPTU says Dublin Bus is exaggerating the amount the company has lost because of the bus strike.
The company has said it has already lost more than €4m.
But Owen Reidy of SIPTU says they were told it would be less: "I hear Dublin Bus say they have lost €4m in three days of action, when we had talks with them they told us it is €600,000 a day because they save on fuel and labour costs.
"So I think we need to look at the facts of this, we are prepared to negotiate, we are prepared to concentrate but we need the other side to do likewise."
Meanwhile, Sinn Féin's demanding the Transport Minister Shane Ross get involved in the dispute.
Dublin Central TD and deputy leader Mary Lou McDonald: "Talks need to happen, it has to be sorted out.
"It can only be sorted out by a management engagement, a union engagement and the Minister making it very very clear that prolonged disputes on the bus service are not tolerable and he will not stand idly by and allow this to continue."