The Dow Jones industrial average fell 0.2 percent, the broad S&P 500 index fell 0.4 percent and the tech-heavy Nasdaq composite index fell 0.8 percent.
On Tuesday, difficult-to-assess information continued to come from US President Donald Trump and from Tehran about possible progress in negotiations on the Iran war.
"What we're seeing right now is a lot of uncertainty about Iran," Terry Sandven, chief equity strategist at US Bank, told CNBC.
The oil price rose 3.6 percent, and a barrel of North Sea oil now costs $103.50.
Technology company Corning was one of the day's winners, rising 8.5 percent after the market suddenly saw signs that the stock was undervalued.
