US President Joe Biden on Wednesday chastised the oil industry over soaring fuel prices at the heart of 40-year high inflation, warning of unspecified emergency measures, AFP reported.

The letter, sent to seven major oil corporations, was Biden's most direct salvo yet in a campaign to blame the industry for stoking price increases.

Average fuel prices are now $5 a gallon for drivers in the United States, up from $3 a year ago, and the spike is reverberating through the entire economy, helping to sink Biden's approval ratings to below 40 percent.

"Refinery profit margins well above normal being passed directly onto American families are not acceptable," Biden wrote in the letter to executives from Shell, Marathon Petroleum Corp, Valero Energy Corp, ExxonMobil, Phillips 66, Chevron and BP.

Biden said the economy is in "a time of war," referring to the global fallout from Russia’s invasion of Ukraine and subsequent sanctions against energy exporter Russia.

"The crunch that families are facing deserves immediate action. Your companies need to work with my Administration to bring forward concrete, near-term solutions that address the crisis," he wrote.

Biden's Democratic Party risks a heavy defeat, losing control of Congress, in November elections, and polls show that fears over the economy dominate.