Those electronics "are just moving to a different Tariff 'bucket,'" Trump said in a social media post.
"We are taking a look at Semiconductors and the WHOLE ELECTRONICS SUPPLY CHAIN in the upcoming National Security Tariff Investigations."
The White House had announced the exclusions from steep reciprocal tariffs on Friday.
Trump's commerce secretary, Howard Lutnick, earlier on Sunday said that critical technology products from China would face separate new duties along with semiconductors within the next two months.
The exclusions announced on Friday were seen as a big break for technology firms such as Apple and Dell Technologies that rely on imports from China.
Trump's back-and-forth on tariffs last week triggered the wildest swings on Wall Street since the COVID pandemic of 2020. The benchmark Standard & Poor's 500 index is down more than 10 per cent since Trump took office on January 20.
Lutnick said Trump would enact "a special focus-type of tariff" on smartphones, computers and other electronics products in a month or two, alongside sectoral tariffs targeting semiconductors and pharmaceuticals.
The new duties would fall outside Trump's so-called reciprocal tariffs, under which levies on Chinese imports climbed to 125 per cent last week, he said.
"He's saying they're exempt from the reciprocal tariffs, but they're included in the semiconductor tariffs, which are coming in probably a month or two," Lutnick said in an interview on ABC's This Week, predicting that the levies would bring production of those products to the US.
"These are things that are national security, that we need to be made in America."
Beijing increased its own tariffs on US imports to 125 per cent on Friday in response.
On Sunday, before Lutnick's comments, China said it was evaluating the impact of the exclusions for the technology products implemented late on Friday.
"The bell on a tiger's neck can only be untied by the person who tied it," China's Ministry of Commerce said.
Billionaire investor Bill Ackman, who endorsed Trump's run for president but who has criticised the tariffs, called on him to pause the broad and steep reciprocal tariffs on China for three months, as Trump did for most countries last week.
If Trump paused Chinese tariffs for 90 days and cut them to 10 per cent temporarily, "he would achieve the same objective in causing US businesses to relocate their supply chains from China without the disruption and risk", Ackman wrote on X.
US Senator Elizabeth Warren, a Democrat, criticised the latest revision to Trump's tariff plan, which economists have warned could dent economic growth and fuel inflation.
"There is no tariff policy - only chaos and corruption," Warren said on ABC's This Week, speaking before Trump's latest post on social media.
In a notice to shippers late on Friday, the US Customs and Border Protection agency published a list of tariff codes excluded from the import taxes. It featured 20 product categories, including computers, laptops, disc drives, semiconductor devices, memory chips and flat panel displays.
Ray Dalio, the billionaire founder of the world's biggest hedge fund, told NBC's Meet the Press that he was worried about the US sliding into recession, or worse, as a result of the tariffs.
"Right now we are at a decision-making point and very close to a recession and I'm worried about something worse than a recession if this isn't handled well," he said.
