Rolls-Royce is to close its plant on Merseyside with the loss of more than 200 jobs.
Workers make turbines for the gas and oil industries
The company has said production is to be moved from the site on Dunnings Bridge Road in Bootle to the US.
The firm has blamed the strength of the pound in its exchange rate with the US dollar and high costs for the decision.
Union representatives said they are "shocked" at the news and have said they will do "everything in their power" to stop the closure of the site.
The company, which makes turbines for the gas and oil industries, said it has been concerned about the future of the plant since August.
But it added no final decision will be made until a consultation process has been completed, which is expected in the new year.
Rolls Royce does said it has tried alternatives to the problem but no viable long-term solution was found.
The union Unite said it will launch a major campaign to save the plant and will be calling for support from government ministers and local MPs and the energy industry clients the plant serves.
Debbie Brannan, Unite regional officer, said: "We are shocked, but not surprised by the company's plan to close its Merseyside plant but this is the beginning of our fight back, not the end.
"Our campaign to save the plant will reach out to Westminster and to industry and we will also be seeking the council and local people's support to keep the plant going."
"We will do everything in our power to stop the closure of the site and we ask the people and politicians of Merseyside to join us in doing the same."
Unite is calling for meaningful negotiations with Rolls-Royce on possible alternatives to closure.
If a decision is made to move forward with the closure proposal, it is expected the facility will close late in 2008.