Ford has cut how much lithium it will purchase from Liontown Resources as a slowdown in electric car sales in North America adds to pressure on the cash-burning Gina Rinehart-backed West Australian miner.

Liontown told investors that its cash balance had fallen 10 per cent over the past three months as weak lithium prices ensured revenues could not cover the ongoing cost of building an underground mine at Kathleen Valley, about 800 kilometres north-east of Perth.