United Co. Rusal International PJSC can’t access its share of alumina from an Australian joint venture, adding to growing pressure on the Russian aluminum giant to find the raw materials it needs to feed its plants.

While Australia banned exports of alumina and related products to Russia a week ago, it was unclear whether Rusal would still be able to take ownership of its share of production from the joint venture with Rio Tinto Group, and potentially ship it elsewhere. That has not been the case, according to people familiar with the matter, who asked not to be identified discussing private information. 

Aluminum is produced in two main stages: raw ore—called bauxite—is refined into alumina, a white powder, which is then smelted at high temperatures to make finished metal. While the aluminum industry hasn’t been directly targeted by sanctions, Rusal’s access to raw materials is under growing pressure as a result of the war in Ukraine, raising questions about whether it can sustain production levels.

Rusal’s alumina supplies from its key Ukrainian refinery have already been “severely curtailed” because of the war, and the company is looking for alternative supply sources. Some 30,000 tons of alumina have been loaded onto two vessels headed for Siberia after leaving China in recent weeks, traders familiar with the matter said last week.

Australia, which supplies nearly a fifth of Russia’s alumina, announced a ban on shipments to Russia on March 20.

Rusal owns a 20% stake in Queensland Alumina Ltd., which is operated by Rio Tinto, and is entitled to the same proportion of production. It is currently unable to access the metal and there is no indication that the situation will change soon, said the people.

Rusal’s press service didn’t immediately comment on Monday. A Rio spokesman declined to comment.