The tariffs affect 5,745 items, down from just over 6,000 in the original proposal. Rare earth elements and antimony have not been included, despite continued industry speculation in the last few weeks.

The Trump administration’s decision not to impose tariffs on China’s rare earths — which are used in used in magnets, radars and consumer electronics — may reflect US dependence on China’s supplies. China accounts for 80-90pc of global rare earth supply, making it unlikely that US consumers could find alternative suppliers.

Impact varies

Participants in other markets are gauging the impact of the tariffs. Chinese bismuth exporters are watching for signs of how the tariffs will affect their business, as China is a major exporter to the US. China exported 1,912t of the minor metal to the US in 2017, accounting for 17.57pc of China’s total exports.

The 10pc tariff is likely to prompt US consumers to seek supplies from other producers in North America. Some may look to continue to buy Chinese material through special routes, such as shipping the metal via Vietnam, to avoid the 10pc tariff.

Exports of calcium-silicon alloy to the US are likely to continue despite the tariff. US consumers rely on China because of supply reductions from Brazil and limited production in Argentina, which is unable to meet the US demand. This means the tariff is likely to lead to a rise in prices in the next few months.

But China’s exports of ferro-silicon alloy will not be much affected, as the country only exports 10,000 t/yr to the US. The new tariff, on top of China’s existing 25pc export duty, will push US consumers to buy material from other countries such as Brazil and Norway. A new plant with 300,000 t/yr of capacity is due to come on stream this year in Malaysia, adding another supply option.

The impact of the tariffs on China’s magnesium and silicon exports will also be limited because the US had already imposed heavy anti-dumping duties on most Chinese producers.

China’s ferro-vanadium exports to the US have dried up in the last few years after anti-dumping duties were imposed in 2012. Chinese suppliers had been selling the alloy to the US via South Korea to avoid the duties since 2002 until the US imposed a 54.69pc duty on imports from South Korea in 2017.

Exports of manganese alloys to the US will be largely unaffected. China’s existing 25pc export duty has already reduced China’s exports sharply in the last decade.

Wider fallout feared

And the new tariffs will not have an immediate impact on battery metals, including nickel, cobalt, lithium, and manganese, as China exports few of these products to the US. But producers have expressed concerns over the knock-on impact of the trade dispute between the two powers, which risks hitting the world economy and affecting demand for battery metals.

The US tariff on China’s exports of germanium is likely to be offset by a rise in the export tax rebate from 5pc to 9pc that took effect on 15 September.

Exporters of gallium metal are observing how the tariff will affect the market, given China accounts for around 14pc of US imports. The impact may be tricky to assess, as the US will only levy tariffs on wrought gallium while unwrought metal was left off the final list. Suppliers are likely to find ways to export wrought metal by classifying it as unwrought metal during the customs clearance process. China’s exports of wrought metal to the US were 7,971kg in 2017, or 11.2pc of its total exports of the product.

The US will also impose tariffs on tungsten fabricated products, such as wire and cemented carbide cutting tools and ferro-tungsten. China’s exports of fabricated products remain small, and it is unlikely that US consumers will be able to find alternative suppliers for ferro-tungsten outside China in the short term. Around 80pc of US ferro-tungsten imports are from China.

The trade war could escalate even further if an agreement is not reached soon. The US will immediately move to impose tariffs on all remaining imports from China — another $267bn/yr — if China takes retaliatory action against US farmers or other industries, the White House said.