Statistics from the Energy Department on Monday show that 298.7 million barrels were in the reserve last week - 6.1 million barrels fewer than in the previous week, CNBC reports.
After the US and Israel launched a war against Iran on February 28, President Donald Trump ordered the release of 172 million barrels in March. A number of other countries also took similar steps.
There is still no clear end to the conflict and global oil reserves are severely strained by the war.
David Goldwyn, who was envoy for international energy issues under President Barack Obama, says he is not concerned about the stability of the reserve, even if a further reduction were made.
