The Strategic Petroleum Reserve fell to 340.3 million barrels, 8.9 million barrels fewer than in the previous week, according to weekly figures from the US Department of Energy, AFP reports.
The level is the lowest since July 1983.
According to the ministry, the war between the US and Iran has slowed crude oil supplies.
The US's dwindling stocks are also linked to countries around the world coordinating a historic release of oil reserves to mitigate the effects of the war.
On Monday, President Donald Trump claimed that oil shipments through the Strait of Hormuz, which Iran had blocked, had begun to resume after an agreement between the countries.
