US aluminium premiums have jumped to their highest in three months after Alcoa announced plans to idle the bulk of its US smelting capacity, stirring speculation among traders that the market may have turned a corner.

Spot CME Midwest premiums rose to 8 cents/lb on Monday for the biggest one-day jump in months as traders scrambled to secure metal in anticipation of lower domestic output even as global inventories are plentiful.

Worries about waning demand from China, the world’s top producer, also linger.

Premiums were firm around 7.9 cents on Tuesday.

On Monday, one of the world’s leading aluminium producers announced it would curtail production at three of its four US smelters, slashing annual capacity by 500,000 tonnes. The rise in surcharges, paid on top of the benchmark London Metal Exchange price, will offer some comfort to traders and producers hit by the unprecedented plunge in premiums earlier in the year as rising Chinese exports and the release of aluminium from financing deals in warehouses flooded the market.

But it is far cry from the 24 cents seen in January, and LME prices remain close to or below breakeven for most producers.

Still, combined with planned cuts by Century Aluminium, the curtailments will remove more than 900,000 tonnes of capacity from the market.

That is a whopping 20 per cent of US consumption that will need to be replaced by imported metal in the future, increasing shipping costs and boosting premiums.

“We’ve seen a bottom in premiums, and the trend is now going to be up over the next several months,” said Lloyd O’Carroll, senior analyst with CRU Group in Richmond, Virginia.

Spot activity was quiet as end-users draw down existing inventories near year-end, but spot market premiums may rise further in the New Year, traders said.

In addition to growing imports of Chinese semi-fabricated products, aluminium shipments from West Asia, where Alcoa runs a massive 760,000 tonne-per year smelter in Saudi Arabia, have ballooned this year.

Saudi Arabia shipped 66,290 tonnes of aluminium to the United States in the year through August, up from 2,700 tonnes in the same period the prior year, US government data show. Exports from the United Arab Emirates and Bahrain also grew substantially.

It costs 9-12 cents a pound to ship aluminium from the Persian Gulf, compared with 4-5 cents a pound from Canada, the United States’ largest supplier, O’Carroll said.