Stocks Fall Amid Oil Price Swings and Rising Treasury Yields

Nvidia's decision to boost its share buyback authorization by $150 billion has led to an increase in shares of Nvidia, but not enough to offset the decline in major stock indexes.

The Nasdaq Composite fell 248.34 points, or 0.9%, to 26,820.38, while the S&P 500 dropped 59.72 points, or 0.8%, to 7,683.69.

Oil prices initially rose in response to US President Donald Trump's rejection of a proposal from Iran that would reopen the Strait of Hormuz, but then fell back as hopes for Middle East negotiations were renewed.