Apple shoppers could face price rises of between 10 and 25 per cent as US President Donald Trump threatens to double the size of his trade war with China in a $US500 billion ($703 billion) conflict that has sent markets spinning.

Australia's chairman of the Joint Standing Committee on Treaties, Stuart Robert, urged Mr Trump to back down from the all-out escalation between the world's two superpowers which would see a tariff applied to almost every product bought by the US from China.

"Australia would like for the US to act in accordance with their World Trade Organisation obligations," said Mr Robert, now the Assistant Treasurer. "We are very a strong supporters of the rules-based architecture."

Apple has written to the US trade department. Credit:AP

Two of the world's largest companies, Apple and Intel, have warned in letters to the US Trade Department that the tariffs would hit the US economy hardest and drive up prices for consumers for goods made with Chinese products.