Guinness management and the company's Joint Union Forum - representing five of the six Guinness unions - will attend talks at the Labour Relations Commission tomorrow in an effort to avoid strike action on Thursday.
Strike notice by the unions was served on Guinness last week following the proposed closure of the firm's packaging plant in Dundalk later this month with the loss of 140 jobs.
If it goes ahead the strike is likely to seriously threaten the supply and distribution of the company's products.
Mr John Kane of SIPTU told ireland.com: "Unions at the company had never before accepted compulsory redundancy and they feared such an action may set a precedent."
He said the unions were also disputing the reasons behind the proposed closure. He said the plant at Dundalk was substantially more cost-effective than the company was alleging.
Mr Kane said if no breakthrough was achieved before Thursday all major Guinness production and distribution outlets would be picketed from 6 a.m.
Guinness spokesman Mr Pat Barry said it was an accepted fact that there was over-capacity in the company's packaging business.
By maintaining the Belfast operation and closing the Dundalk plant the company would save around £8 million annually, he said.
He said the decision to close the plant reflected global economic conditions and was not part of any grand rationalisation plan.
