Well-supplied markets and weakening demand for crude concern American drillers.

The U.S. crude oil price benchmark, West Texas Intermediate, fell 8% to less than $68 a barrel, the lowest level since last week. The global Brent crude price benchmark likewise fell about 8%. Major stock indexes ended the day in positive territory.

Key Takeaways Oil futures surged to a five-month high Monday morning after the U.S. struck Iranian nuclear facilities over the weekend but fell sharply later in the day amid optimism that an escalation of the conflict in the Middle East could be avoided.