The price of oil has surged on the news of the United States' military strike that killed Iran's top general.
Uncertainty has gripped global investors, who are trying to gauge what Iran's response will be.
In previous tensions with the U.S., Iran has threatened the supply of oil that travels from the Persian Gulf to the rest of the world.
About 20% of oil traded worldwide travels by ship from the gulf.
Analysts say Iran is expected to respond to the killing but perhaps not immediately.
The international benchmark for crude oil jumped 4.1%, or $2.70, to $68.95 a barrel on Friday.
NYU professor Nouriel Roubini tweeted early Friday the U.S.-Iran conflict is "a recipe for the start of a full scale hot war engulfing the Gulf & spiking oil prices."