Apple iPhones would be around $100 more expensive in the US once new 10 per cent tariff on $300 billion in goods imported from China comes into place from September 1.

"iPhone sales in the US, China and other markets could fall by 8 million to 10 million," CBS News reported late Friday, quoting analysts.

Apple lost $42 billion in stock value after Trump tweeted new tariffs on China on Thursday.

Apple XS Max starts at $1,099 and new 10 per cent tariff would mean a roughly $110 hike.

Trump escalated his trade war with China by announcing that he would impose a fresh 10 per cent tariff on another $300 billion of Chinese goods that will take effect from September 1, prompting a swift rebuke from Beijing and jolting global financial markets.

The development comes after the latest round of talks, led by US Trade Representative Robert Lighthizer and Treasury Secretary Steven Mnuchin with Chinese delegation headed by Vice Premier Liu He in Shanghai, showed little sign of a breakthrough.

The duty is likely to target a wide range of goods, from smartphones to clothing.

Trump also said that tariffs could be lifted further in stages to more than 25 per cent.

Over the past year, China and the US have imposed tariffs on billions of dollars of one another's goods.