Reacting to the US Supreme Court ruling on Friday that threw out tariffs it deemed were illegally justified on grounds of an emergency, Trump initially announced a new temporary global tariff of 10 per cent.
He said on Saturday he would increase it to 15 per cent.
But in a notice described as intended to "provide guidance regarding the February 20, 2026 Presidential Proclamation", the US Customs and Border Protection said that, aside from products covered by exemptions, imports would "be subject to an additional ad valorem rate of 10 per cent".
The move added to confusion surrounding US trade policy, with no explanation offered in the notice for why the lower rate had been used.
The Financial Times quoted a White House official as saying the increase up to 15 per cent would come later.
Reuters could not immediately confirm this.
"Remember that Trump is delivering the State of the Union address tonight, so it's possible we might get a better sense of the next steps on tariffs," Deutsche Bank analysts said in a note.
The new tariffs took effect at midnight on Tuesday, while collection of the tariffs annulled by the Supreme Court was halted.
They had ranged from 10 per cent to as much as 50 per cent.
It remains unclear whether and how companies will be refunded for tariff payments made under the regime annulled by the Supreme Court.
The Section 122 law allows the president to impose the new duties for up to 150 days to address "large and serious" balance-of-payments deficits and "fundamental international payments problems".
Trump's tariff order argued that a serious balance-of-payments deficit existed in the form of a $US1.2 trillion ($A1.7 trillion) annual US goods trade deficit, a current account deficit of 4 per cent of GDP and a reversal of the US primary income surplus.
Trump on Monday warned countries against backing away from any previously negotiated trade deals with the US, warning he would hit them with much higher duties under different laws.
Japan said it had asked the United States to ensure its treatment under a new tariff regime would be as favourable as in an existing agreement.
The European Union, Britain and Taiwan indicated a preference to stick to their deals, too.
China, meanwhile, urged Washington to abandon its "unilateral tariffs", indicating it was willing to hold another round of trade talks with the world's largest economy, the country's commerce ministry said in a statement on Tuesday.
