U.S. President Donald Trump has announced a national security trade investigation into the semiconductor sector, indicating that smartphones, computers, and other electronics will face new tariffs. The exclusions from reciprocal tariffs on China announced on Friday were seen as a break for technology firms such as Apple and Dell. Trump's back-and-forth on tariffs last week triggered volatile markets, with the S&P 500 index down more than 10% since he took office. Billionaire investor Bill Ackman has called on Trump to pause the tariffs on China for three months to avoid disruption and risk.