The company posted its fourth-quarter results on Thursday and Alcoa president Roy Harvey said during an earnings call in the US that the Portland smelter would continue to produce aluminum until at least mid-2021, the Australian Financial Review reported.

A four-year federal-state package was struck for the site in January 2017 and is due to expire in mid-2021, with high power prices sparking speculation about the site's future.

"'You will not see action," Mr Harvey said. "In fact part of that agreement is that we would not take action until the middle of 2021."

Australian Manufactures Union Victorian secretary Ben Davis said the financial results would worry workers.

"They can be confident they are going to have a job for the next year," Mr Davis said.

"The smelter has been remarkably resilient in remaining calm and going on. But you can't see international profit results like that and not be nervous."

Mr Davis said there was hope the site could secure government subsidies and cheaper power in the next 18 months.

"The fact energy in Victoria is more expensive than anywhere in the world, is troubling ... Alcoa and the state and federal governments need to pull together tot get a new power deal," he said.

The site is Victoria's biggest power consumer and employs about 460 people directly and has about 190 contractors.

"It is a modern smelter. The difficulty today is renewables can't provide enough base-load supply to power a smelter, but renewables will get there over the next couple of years," Mr Davis said. "The question is how do we bridge that gap?"

Mr Davis sad the workers had shown perseverance while recovering the smelter from a near fatal power outage last November.

"They've been terribly good about going to work and doing their thing. And full credit to them for that," Mr Davis said.

South West Coast MP Roma Britnell called for the state government to secure every job at the smelter.

"There is no way I am giving up on Alcoa and the role it plays in our region," she said.

"Aluminum is in high demand across the world, if we close down Alcoa in Victoria it will be up somewhere else in another country that might not have the environmental considerations we can demonstrate."

A state government spokeswoman said any arrangements between Alcoa and power companies are a matter for those private companies.

Ms Britnell said the government could not shy away from its involvement in power prices.

"Daniel Andrews says it is up to Alcoa, but what we all know is that manufacturing relies heavily on power being affordable, and the direct action of the Andrews government has led to a power station closing early without renewable or base-load power to ensure there is a reasonable supply," she said.

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