A barrel of North Sea oil now costs $104, after rising almost 4 percent in futures trading during the day.
The White House’s plans for new attacks on Iran, the fighting in Yemen and attacks by Iran-backed rebels on Saudi Arabia loom in the background.
Interest rates on US government bonds are also rising sharply, with the 10-year rate reaching its highest level since 2002.
In addition, the Federal Reserve has signalled its willingness to raise interest rates soon, if necessary, to curb stubborn inflation.
After a few minutes of trading, the Dow Jones Industrial Average was down 0.2 percent, the broad S&P 500 index was down 0.3 percent and the tech-heavy Nasdaq Composite was down 0.5 percent.
