In early trading, all major indices fell amid the US and Israel's war against Iran, which continued with high intensity.
However, when President Donald Trump announced late at night that the United States would offer an insurance solution for ships in the Strait of Hormuz, which Iran had closed, the market calmed down somewhat.
At the close, the Dow Jones Industrial Average had fallen 0.8 percent, while the broad-based S&P 500 index lost 0.9 percent and the tech-heavy Nasdaq Composite Index fell 1 percent.
The decline on leading European stock exchanges is even greater. The DAX index is down 4.0 percent, the CAC 40 in Paris is down 3.2 percent and the London Stock Exchange's FTSE index is down 2.9 percent.
The price of oil also turned downward in the wake of Trump's promise, and at the close of trading, the price of a barrel of Brent oil was just over $81, compared with Tuesday's peak of around $85.
