Some of the world's biggest footwear firms are urging Donald Trump to end the US trade war with China, warning of a "catastrophic" effect on consumers.In a letter signed by 170 companies, including Nike and Adidas, they said the President's decision to lift import tariffs to 25% will disproportionately impact the working class.They also warn that higher levies threaten the future of some businesses."It is time to bring this trade war to an end," the firms urged.Mr Trump lifted levies on $200bn worth of Chinese imports into the US from 10% to 25% more than a week ago after Washington and Beijing failed to reach a deal on trade.China retaliated by announcing plans to raise levies on $60bn of US imports from 1 June.The footwear companies who signed the letter, including Clarks, Dr Martens and Converse, claim that while the average US tariff on footwear is 11.3%, in some cases it can reach as high a 67.5%."Adding a 25% tax increase on top of these tariffs would mean some working American families could pay a nearly 100% duty on their shoes," the companies wrote."This is unfathomable."When he lifted tariffs earlier this month, Mr Trump told companies that they could reduce costs by shifting production to the US.However, the shoe-makers and retailers say that while they have been moving their sourcing away from China: "Footwear is a very capital-intensive industry, with years of planning required to make sourcing decisions, and companies cannot simply move factories to adjust to these changes."The US and China are set to meet again to discuss trade at the G20 summit in Japan next month.In the meantime, however, the US has increased pressure on China by declaring a national emergency to protect US computer networks from "foreign adversaries", affecting Huawei, the Chinese telecoms giant.