Unofficial pickets at two Gama Construction sites in Dublin are to continue after the failure of moves to get the parties into talks at the Labour Relations Commission (LRC).
Nearly 300 of the company's Turkish workers have been engaged in a stoppage for the past five weeks in a row over their pay and conditions.
Gama and Siptu yesterday blamed each other for the continuing stalemate in the dispute.
The LRC has invited the parties to attend conciliation talks, as long as the unofficial industrial action at the sites in Balgaddy and Ballymun is called off.
Siptu national organiser Noel Dowling said the union's members at Gama were prepared to return to work to facilitate the talks process.
Before that could happen, however, the union wanted the LRC to chair exploratory talks "in order to agree issues surrounding a return to work".
Gama Construction says picketing must stop before it attends the LRC for discussions, exploratory or otherwise.
Mr Dowling said the LRC had issued an invitation to both parties to engage in exploratory talks, followed by talks on the substantive issues.
He criticised the company for refusing to enter talks on that basis.
"It is the firm view of Siptu that Gama management are engaged in a war of attrition directed at ensuring that workers are forced to give up their month-long struggle for justice and that the company will never be held to account for the millions of euro still owed to its workers in return for up to 80 hours' work per week," he said.
Gama responded with a statement in which it said it had consistently advised the Labour Relations Commission that, if the picketing of sites were stopped, it would be prepared to enter exploratory and substantive talks.
"That offer was repeated this afternoon when the company proposed to meet at the LRC next Tuesday.
"Gama continues to make itself available for talks in the event that pickets are lifted," the statement said.