Washington DC - President Donald Trump caused more global economic confusion as he announced an expansion and date change for tariffs he imposed on imported trucks.

Tariffs that were set for October 1 and only supposed to affect heavy-duty trucks have been pushed back to November, but will now target medium trucks as well, Trump said in a Truth Social post Monday.

The 79-year-old had initially unveiled the tariffs in September, as part of a larger package of measures.

It was not immediately clear whether the new 25% levy would be added on top of existing duties, such as country-specific rates.

Imports from the European Union to the US, for example, are currently subject to a base tariff rate of 15%.

The president has justified his actions on "national security" grounds, offering no further details or justification for his claims.

Trump has unleashed a tariff war on friend and foe alike since returning to office in January, arguing that the US economy is suffering after years of being "cheated" by other countries. His unprecedented and chaotic actions have faced multiple legal challenges, with the Supreme Court set to rule on whether he overstepped his authority by invoking a national emergency to impose the duties.

Per Fox Business, almost three quarters of all US freight is transported by trucks, making the industry a cornerstone of the domestic economy.