Oil prices surged by as much as 19% before coming off peaks after the biggest intraday jump since the 1991 Gulf War.
An attack on Saudi Arabia shut 5% of global crude output.
U.S. officials blamed Iran and President Donald Trump said Washington was "locked and loaded" to retaliate.
Prices eased after Trump announced that he would release U.S. emergency supplies, and producers around the world said there were enough stocks stored up to make up for the shortfall.
Saudi Arabia's oil output will be fully back online quicker than initially thought following weekend attacks on production facilities.
Up next are the weekly Inventory numbers from the government's Energy Information Administration (EIA) due at 1430 GMT.
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