President Trump is considering banning or restricting diesel exports to lower surging domestic prices weeks before the midterm elections. But experts say the policy may not lower prices for long and could backfire by prompting U.S. refineries to make less diesel, raising costs again.

Diesel averaged $6.51 a gallon Thursday, up from $3.69 a year ago, according to the AAA motor club. Prices rose after Israel and the United States began attacking Iran nearly seven months ago, disrupting global energy, while Ukrainian attacks on Russian refineries also pushed up fuel prices.

Experts say Mr. Trump may have emergency authority to restrict exports, but it is unclear whether he could impose a complete ban alone. Jason Bordoff of the Center on Global Energy Policy at Columbia University noted that 2015 legislation clearly covers crude oil but not refined fuels like diesel. Congress could act, though the House is not scheduled to return before November.

Energy secretary Chris Wright said the administration was not considering a full ban. The United States produces about 5.3 million barrels a day of distillate fuels, with domestic use typically accounting for 70 percent and exports making up the rest.