Wall Street retreated as investors weighed renewed trade tensions and an ongoing sell-off in software stocks driven by unease over artificial intelligence valuations. The S&P 500 and the tech-heavy Nasdaq Composite each slid by more than 1%, extending losses that have unsettled equity markets in recent weeks.

The downturn followed an announcement by Donald Trump imposing blanket global tariffs of 15%, hours after the Supreme Court of the United States struck down much of his earlier levy framework. The president warned that countries that “play games” could face steeper duties. Earlier in the day, the European Union paused ratification of its trade agreement with Washington, adding to the sense that a broader commercial standoff may be brewing.