Donald Trump has launched an attack on Apple's plea for tariff waivers for its new computers.

"Apple will not be given Tariff wavers, or relief, for Mac Pro parts that are made in China. Make them in the USA, no Tariffs!" he wrote.

Earlier this week, Apple asked the Trump administration for a tariff exemption for the parts for its new Mac Pro computers that are being made in China. Without that exemption, the company could be charged considerable duties of 25 per cent to bring those parts into the US.

Those costs are likely to be passed on to the consumers who buy the products. The Mac Pro is already one of the most expensive products Apple has ever announced, with a monitor stand that costs $999 on its own.

The tariffs are part of the US and China's growing trade war, which has seen heavy tariffs placed on products that are traded between the countries.

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The affected parts include the computer's frame, its power supply, the cables and circuit boards that are inside it and the optional wheels that users can buy to push it around, according to a report from Bloomberg. It also asked for exemptions on accessories such as the mouse and USB cables.

Apple already got exemptions from the Trump administration for some of its other products, including the iPhone and the AirPods. But the Mac Pro is yet to go on sale and the company will need specific exemptions for those parts if is to avoid the heavy tariffs.

The US government has indicated that companies will be able to get exemptions from the tariffs if they can prove that the parts can only be built in China and don't have any strategic use to China.

But Mr Trump has always insisted that companies should try and make their products in the US if they wish the avoid the tariffs.

When Apple revealed the previous Mac Pro, in 2013, it proudly boasted that it would be assembled in the US and it has been made in Texas ever since. But a completely re-designed version of the computer was announced last month, and that computer is said to be made in China.

Apple's shares had been gaining through the day but quickly dropped back after Mr Trump sent his tweet.