The contract relates to the aluminium company's Hawesville smelter in Kentucky, which may now close if keeping it open is no longer economically viable.

Century's president and CEO Michael Bless, said: "Our smelter in Hawesville is a great plant, operated safely and efficiently by a superb group of employees. It is competitive on the global market in every category other than the price we pay for electric power, which is among the highest such rates for smelters in the US. The unavoidable truth is that the smelter is not economically viable with this power rate and under current market conditions. We need a power price that is reflective of the market, helps the plant weather these turbulent economic conditions and allows the plant to be competitive over the long term," he said.

According to Bless, "We fully understand the devastating impact that the plant's closure would have on our employees, customers and suppliers, as well as on Kentucky's economy. We are fully committed to exploring all available options to keep the smelter open both in the short-term and long-term."

Bless said he hoped to reach an agreement to save the smelter and protect 700 jobs.

Century is required to pay a demand charge for power, but is under no obligation to keep the plant open.