'Oil accelerated a months-long slump after Saudi Arabia cut its prices for U.S. buyers in an effort to counter the shale boom.
The move coincided with an increase in prices for Asia and Europe, signaling Saudi Arabia's intention to grab a bigger share of the American oil market. It also suggests Saudi Arabia may be looking to squeeze U.S. oil producers, who are already under mounting pressure from falling oil prices.
Foreign producers like Saudi Arabia, the world's largest exporter of crude, have lost some influence in the U.S., where a surge in shale oil output is reducing the need for imports.
"I think it's a moral equivalent of war on the U.S. oil producer. That's exactly what it is, and Saudi Arabia is not trying to hide it," Phil Flynn, a senior energy analyst at Price Futures Group, said on "Opening Bell with Maria Bartiromo."