US stocks slumped on Monday, weighed down by escalating Middle East tensions and rising oil prices. Traders boosted bets on interest-rate hikes, putting pressure on equities. The S&P 500 Index closed 0.3% lower, though it posted its best August since 2021, rising 2.6% this month.

The Nasdaq 100 Index rose 0.1%, finishing 4.2% higher in August and snapping two straight months of losses. Nine of the 11 S&P sectors fell, led by a drop in communication services and utilities. The Dow Jones Industrial Average also declined.

Market sentiment remained fragile as geopolitical risks and monetary policy expectations dominated trading activity. Investors closely monitored developments in the energy sector and Federal Reserve signals for further direction.