HOUSTON — As domestic gasoline prices surged to their highest level in three years, President Trump railed against the OPEC oil cartel on Friday, declaring that the group was unjustifiably manipulating supplies for selfish gain.
“Looks like OPEC is at it again,” Mr. Trump wrote on Twitter. “Oil prices are artificially Very High! No good and will not be accepted!”
The Organization of the Petroleum Exporting Countries makes an easy scapegoat for American politicians. It has been a target of derision by American leaders since the Arab oil embargo of 1973 caused long lines at the pump and badly damaged the economy.
But OPEC doesn’t have the same influence it once did, given soaring production in the United States, Canada and a few other countries. Now it is just one factor in lifting prices, which are being affected by everything from geopolitics to the growing demand for gasoline and diesel fuel.
Mr. Trump could have been referring to OPEC’s cutback in exports to increase prices. Saudi Arabia and other oil producers in the region have also made an alliance of convenience with Russia, a non-OPEC member heavily dependent on oil revenues to finance its government. Together they have restrained production since 2016, reducing global stockpiles.
“Prices are high,” said Rob West, an analyst at Redburn, a London research firm. Noting that Mr. Trump may have a point, he added, “I do see some artificiality in the prices we see today.”
OPEC and non-OPEC producers gathered Friday in the Saudi city of Jidda in an effort to continue the policy even as the price of Brent crude, the global benchmark, has climbed above $70.
Not long ago, as prices plummeted from over $100 a barrel in 2014 to below $30 in early 2016, inventories were so high that tankers were needed to hold excess supplies. Now, even as United States oil production continues to grow, worldwide inventories are declining, increasing the pressure on prices. The International Energy Agency reported that global oil supply eased by 120,000 barrels a day in March.
The price of crude is the major reason American drivers are paying more at the pump as the summer driving season approaches. The average price for a gallon of regular gasoline on Friday was $2.75 a gallon, according to AAA, up 19 cents over the last month and 33 cents from a year ago. It is the highest level since the summer of 2015.
The increase has been particularly noticeable over the last week, with prices in some states rising more than a penny a gallon every day.
Americans consume roughly 400 million gallons of gasoline a day, so the 33-cent increase over the last year means roughly $132 million less every day in consumer pockets. Working-class Americans, who usually drive older, less fuel-efficient cars and spend a higher percentage of their income on fuel, are disproportionately affected.
“This hurts the pocketbooks of typical Trump voters in swing states who live paycheck to paycheck,” said Tom Kloza, global head of energy analysis at the Oil Price Information Service. He predicted gas prices would continue to increase modestly, probably rising above $2.80 a gallon in the coming weeks.
Mr. Trump’s comments may have been informed by his new top economic adviser, Larry Kudlow, who has long viewed low gasoline prices as a beneficial stimulus. In a 2014 commentary for CNBC.com, he argued that lower oil prices would produce savings for households and businesses, freeing up money for consumers to spend. “All these factors will increase U.S. economic growth, not reduce it,” he wrote.
Deutsche Bank analysts warned this week that the rise in gas prices was beginning to cut into the disposable-income gains from the tax cuts Mr. Trump signed into law late last year.
Much of the recent price increase is a result of world tensions — some related to Mr. Trump’s policies — that have bolstered investor expectations that oil prices could rise even higher.
Oil production is plummeting in Venezuela, the country with the largest reserves, and the expectation of stepped-up American sanctions in the coming months could reduce its exports further. The threat that the United States could pull out of the nuclear deal with Iran has put the size of future Iranian exports in doubt.
Worsening tensions between Saudi Arabia and Iran have added to traders’ concerns. And the illness of a military power broker in Libya threatens more political turbulence and a reversal in the yearlong increase in Libyan exports.
A doubling of American oil production in recent years, producing growing exports and a decline in imports, has helped stabilize the oil market and kept big price rises in check. But United States output represents only a bit more than 10 percent of the 98 million barrels a day produced worldwide, and there are limits to its growth.
A shortage of oil and natural-gas pipelines in Texas could slow output over the next two years. In addition, American refineries, generally designed for heavier crudes, are reaching a saturation point for lighter shale oil produced around Texas and North Dakota.
Still, there is no doubt that the orchestrated output curbs led by major producers have had an effect. It is not clear whether the agreement will be extended beyond the end of the year, but the Saudis appear to favor doing so.
In a statement on Friday, OPEC praised the “high conformity” level with the cuts but implied that continued curbs were needed, saying that “commercial stocks remain above levels seen before the market downturn.”
An earlier version of this article misstated, on one reference, a recent increase in gasoline prices. They have risen 33 cents in the last year, not the last month.