Wall Street sold off amid trade uncertainty after the Supreme Court struck down most of President Trump's global tariffs last Friday. Trump posted on Truth Social Saturday that he would raise worldwide tariffs to a "fully allowed" 15% from 10%, claiming no congressional approval is needed beyond 150 days. He warned countries "playing games" face higher tariffs, while the EU demanded clarity and commitment to the August 2025 Joint Statement.

IBM shares plunged 13.2% after Anthropic's Claude announced COBOL capabilities, pressuring the tech giant's core business data processing segment. The European Commission called the situation "not conducive" to fair transatlantic trade.

Financial stocks turned in some of the market's worst performances, with the KBW Bank Index and the NYSE Arca Securities Broker/Dealer Index plunging by 4.4% and 3.4%. Software stocks were substantially weak, as reflected by the 3.9% nosedive by the Dow Jones U.S. Software Index. Airline, computer hardware and networking stocks too saw a significant weakness while gold stocks bucked the downtrend amid a sharp increase by the price of the precious metal.

Asia-Pacific stocks turned in a mixed performance, with markets in Japan and China closed for holidays. Hong Kong's Hang Seng Index surged by 2.5% while Australia's S&P/ASX 200 Index slid by 0.6%. Meanwhile, the major European markets all moved to the downside on the day while the German DX Index slumped by 1.1%, the French CAC 40 Index dipped by 0.2% and the U.K.'s FTSE 100 Index closed just below the unchanged line.

In the bond market, treasuries moved sharply higher due to their appeal as a safe haven amid the tariff uncertainty. Subsequently, the yield on the benchmark ten-year note which moves opposite of its price, slumped 5.7 bps to 4.02%.