Up to 100 specialist chemical jobs are in the balance after an Anglesey company announced it could close.
The plant has provided Amlwch jobs for more than 50 years
Global giant the Great Lakes Chemical Corporation says it may be forced to shut its Amlwch plant, formerly known as the Octel works.
In a statement, the company said it would begin discussions with employees on the closure.
Site manager Brian Macconnachie said: "These steps are being taken after a careful review of operational costs, increased competitive pressures and market conditions.
"Our employees have worked hard over the years to try to make the plant as efficient and productive as possible.
"Despite our efforts, the Amlwch site remains uncompetitive."
About 100 workers would be affected by the shutdown.
'Stunned and shocked'
Ynys Mon Labour MP Albert Owen is due to meet the site's management.
Local Plaid Cymru assembly member Ieuan Wyn Jones said the community would be "stunned and shocked" by the possible loss of a company which had employed people in the area for more than 50 years.
Mr Jones said such good quality jobs would be very difficult to replace, and called on the Welsh Assembly Government to set up a task force to see whether the jobs could be saved.
If that was not possible, he said the task force should be empowered to try to bring other jobs with the area.
The company said employee discussions were expected to begin within the next 30 days and would be concluded as quickly as possible in accordance with British employment legislation.
Mr Macconnachie said workers would be considered for a limited number of positions at the company's other sites
The firm's only other site in Britain is in Manchester.
Great Lakes Chemical Corporation is one of the world's leading producer of certain speciality chemicals for applications like water treatment, speciality household cleaners and performance chemicals.