The price of oil has risen sharply due to concerns about the situation in Syria.
North Sea Brent crude was $US114.14 per barrel on Tuesday - the highest since February. The price of US crude rose by $US3 to $US108.92 per barrel.
Goldman Sachs has raised its short-term forecast for the oil price to $US115 per barrel.
Syria is not a significant oil producer, but the BBC reports there are fears for the stability of the wider Middle East region, which produces about a third of the world's oil.
Even before the latest developments in Syria, analysts were forecasting higher oil prices, partly because of supply disruptions.
"This is the largest geopolitical risk since the start of the Iraq war," said Jones Trading chief market strategist Mike O'Rourke.
"This war of words with Russia is the first time the United States is pitted against another global (power) in a long time. That creates an uncertainty this market is not accustomed to."
Stocks in the United States had their worst day since June. European markets were also down.
The Dow Jones Index was down 1.14% and the Nasdaq 2.16%.
In London, the FTSE 100 index closed down by 0.8%. The DAX in Frankfurt and the CAC-40 in Paris were down about 2.5%.
