U.S. stocks opened lower Wednesday, with the Dow Jones Industrial Average down 0.15%, the S&P 500 off 0.17% and the Nasdaq Composite declining 0.36%. Selling intensified shortly after the opening bell as investors assessed new U.S.-Canada trade restrictions, elevated Treasury yields and a higher implied probability of a Federal Reserve rate increase in September. By about 9:46 a.m. ET, the Dow had fallen 0.68% to 52,435.25 after touching 52,381.24, while the S&P 500 was down 0.27% at 7,652.80 after reaching 7,646.91. S&P 500 futures had earlier approached 7,690 before reversing toward 7,665. Technical levels highlighted in the supplied charts put initial support near 52,380-52,400 for the Dow and 7,640-7,650 for the S&P 500, with both indexes below their 50-period exponential moving averages. President Donald Trump signed five proclamations under Section 338 of the Tariff Act of 1930 after Canada imposed retaliatory tariffs on about $20 billion of U.S. exports. Selected product changes take effect Sept. 15, while separate import bans begin Sept. 29. CME FedWatch showed a 60.2% probability of a 25-basis-point increase at the Fed's Sept. 16 decision, despite a Reuters survey finding roughly 70% of economists expected rates to remain unchanged. Treasury also said it would at least double the maximum size of liquidity-support buybacks in certain longer-dated securities to at least $4 billion per operation through Nov. 4. Barclays raised its 2026 year-end S&P 500 target to 7,950 from 7,800 but cited inflation, geopolitical uncertainty and tighter monetary policy as risks. Policy developments have moved to the center of market trading, leaving equities sensitive to upcoming inflation and Federal Reserve signals.