US President Donald Trump said he plans to levy an 'approximately' 100 percent tariff "on all chips and semiconductors coming into the United States."

However, companies that are building, or planning to build, in the country will not be made to pay. Timelines for the long-threatened semiconductor tariffs were not shared.

The President did not disclose the level of investment required to be exempt from the tariffs. It is not clear if such investment has to be for semiconductor-related spending, such as Apple's recent deals with Applied Materials and Texas Instruments, or just any spending in the country.

“Even though you’re building and you’re not producing yet, in terms of the big numbers of jobs and all of things building, if you’re building, there will be no charge," Trump said during a press conference.

Trump also claimed that TSMC, the world's largest contract chipmaker, was set to spend $300 billion on its chip fabs in Arizona. The company declined to comment, but in a filing earlier this year, said that it expected to spend $165bn across the US.

It is not known if TSMC's multi-billion dollar investment means that all chips made by the company are immune from tariffs, or if end customers, including server makers and hyperscalers, will need to make their own investment pledges.

Trump also threatened that companies that promised investments and then failed to deliver would be charged with back-dated tariffs.

Tariffs are paid by the importer, not the exporter.