New Delhi, May 21 -- Wall Street's key stock indices ticked downward on Thursday as crude oil prices spiked following news report that Iran's Supreme Leader Ayatollah Mojtaba Khamenei directed the nation's uranium to remain within the country, dampening expectations for a breakthrough in diplomatic talks between Washington and Tehran.

At the opening bell, the Dow Jones Industrial Average fell 25.5 points, or 0.05%, to 49,983.8. The S&P 500 fell 22.2 points, or 0.30%, to 7,410.78​, while the Nasdaq Composite dropped 126.7 points, or 0.48%, to 26,143.616.

Market participants grew increasingly anxious that an extended blockage of the strategic Strait of Hormuz might exacerbate global energy supply shocks and drive up inflationary pre...