"We believe in a long term growth for aluminium. However, in the short term, we are concerned about the macro outlook and the effect for us on aluminium demand," she said.

Hydro until recently expected world aluminium demand excluding China to grow by up to 1% in 2019, but now instead forecasts a decline of 1-2%.

While global demand is still expected to exceed production this year, the market is expected to be more or less balanced in 2020, Aasheim said.

(Reporting by Victoria Klesty, editing by Terje Solsvik)