Talks to save 298 jobs at the Alcoa aluminium plant in Swansea are under way following an announcement that the plant is to close in March.
Alcoa said the announcement came after years of "significant losses"
Welsh Enterprise Minister Andrew Davies said he was deeply disappointed by the news and wanted an "urgent meeting" with managers at the company.
Swansea Council leader Chris Holley has also pledged to work alongside the assembly government in a rescue bid.
The US company has blamed rising energy, labour and materials costs.
The site, bought by Alcoa in 1968, mainly produces aluminium for the drinks container industry.
Mr Holley met senior council officers on Wednesday to consider what support they could offer.
He said: "The planned closure of Alcoa is a body blow to Swansea and the wider region.
The Swansea factory employs 298 people
"Not only are we facing the prospect of losing 300 highly-skilled and well-paid jobs at Alcoa, the planned closure will also hit local suppliers and could affect up to 1,000 jobs.
"The impact on the local economy will be massive and that is why we want to work with Andrew Davies in his efforts to reverse Alcoa's decision."
Mr Holley added: "We will do everything we can to save these jobs."
Mr Davies said he hoped to meet plant manager Alan Griffith later this week to discuss what else the assembly government could do to help keep the plant open.
He said £2m would be made available if the factory stayed open, but a £2.5m grant the firm already received will have to be paid back if it does not.
The minister said: "Certainly we will be making it clear the grant offer would be reclaimable, and I understand the company are aware of that, but obviously I would reinforce that message.
"I am aware that the company has been under huge cost pressure, with rising energy prices - electricity and oil and raw materials - and I know that they have been discussing a cost-cutting package with the unions."
Mr Davies said that he thought there were "grounds for optimism" as the closure at Corus in 2001 which had threatened 3,000 redundancies had seen only around 100 people lose their jobs once the closure went ahead.
Union Amicus said it was "shocked and outraged" at the announcement on Tuesday afternoon, which could lead to the loss of all 298 jobs at the plant.
Union representative Paul Collier said staff working at the plant would be "rightly outraged" at Alcoa's announcement, claiming the company had been turning away orders from customers.
He added: "We believe there are economic measures that we can take within the business - to restructure it or maybe even downsize it. It's important to us to keep this site alive."
Alcoa spokesman Kevin Lowery said the plant had been in financial trouble for some time, but that the planned closure had been a "tough decision".
He told BBC Wales: "Unfortunately, in addition to some overall market conditions going on we have significant losses going on at the plant due to rising energy, high labour costs and material costs."
One Alcoa worker, who asked not to be identified, said: "In south Wales, manufacturing jobs are just disappearing overnight.
"It's not just happening once a year, it's happening week-on-week. The manufacturing sector in this country is on its knees."
Alcoa is to start consultations with employee representatives within the next week.