The Dow Jones Industrial Average extended its decline Monday, closing 628.18 points lower at 52,786.07 as the New York Stock Exchange reopened after a holiday weekend. Crude oil prices climbed amid an exchange of attacks between the United States and Iran, intensifying concerns about accelerating inflation and strengthening expectations for additional U.S. interest rate hikes. Investor sentiment was also weakened by Canada's decision to impose tariffs of up to 50% on imports from the United States in retaliation for steep tariffs imposed by the Trump administration. The Nasdaq Composite fell for a second consecutive session, ending 85.58 points lower at 26,421.41. Amgen and Salesforce recorded notable declines, while Caterpillar attracted buying interest.