CORUS is to halt most production at its Llanwern plant until at least March next year.
It said production will be run down to about ten percent of its current capacity.
But it could not give a cast iron assurance when full production would return - adding that its aim of returning to full production in March was an aspiration.
The plant’s 800 workers will not be laid off and will work on maintenance, engineering tasks and training during the closure.
The Community union, which represents steel workers at Llanwern, said Corus has workers will be paid their shift allowance until Christmas.
It said the firm plans to discuss shift allowances with the union following the Christmas period, and understand that its Zodiac galvanising operation would be up and running again in February.
Corus says slowdowns in construction, car and electrical appliance industries had seen dramatic falls in the demand for steel.
The company is reducing steel production by 30 per cent across Western Europe.
It is currently operating only one furnace at a time in Port Talbot.
Corus spokesman Robert Dangerfield said closure is not on the cards at the plant.
“These things are always an option but its not being considered,” he said.
He said the company does not want to lose the skills of the Llanwern workers, which he described as a “vital resource” for the company.
Community regional director Rob Edwards said Corus bosses had kept their word to the union.
He said: “Our point of view is that there are no redundancies and they are keeping their promise that everyone will receive their full shift allowance until the Christmas period.”
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here