American tariffs on dozens of countries will come into effect next Wednesday as scheduled, although several deals could still be worked out before then, President Donald Trump confirmed Friday.

Trump announced the Vietnam deal on Wednesday, saying that the US would place a 20 per cent tariff on Vietnamese exports to the US and a 40 per cent rate on goods deemed transshipped through the nation — a reference to the practice whereby components from China and possibly other nations are routed through third countries on their way to the US.

US President Donald Trump has threatened to impose a "30% or 35%" tariff on Japan if a deal between the two countries is not reached before a deadline next week. That would be well above the 24% tariff Japan was hit with as part of Trump's so-called "Liberation Day" on 2 April,