Trump's energy secretary has poured cold water on the idea

Diesel prices reached their highest levels on record at $6.53 a gallon on Tuesday, according to AAA.

President Donald Trump said Tuesday that he would back a ban on U.S. diesel exports to help bring down prices. Analysts say such a move would have the exact opposite effect.

"I've said, let's not send out the diesel," Trump said on the sidelines at the United Nations General Assembly in New York, adding that keeping the fuel in the U.S. could help to lower overall gasoline prices. He said a decision by his administration would come "fast, one way or the other."

Trump's comments came as diesel prices in the U.S. reached their highest level on record at $6.53 a gallon on Tuesday, according to AAA, up 75% year over year.

"The problem with export bans is that they don't increase domestic supply, but may lower supply, causing a further rise in prices," said Gbenga Ajilore, chief economist at the Center on Budget and Policy Priorities, a Washington-based think tank.

"Higher diesel prices are a concern, but the main driver of the higher prices is the war in Iran," he said. "End the war in Iran, open up the Strait of Hormuz, and diesel prices will fall. Any other solution will fail."

A day after Trump's comments, his own energy secretary poured cold water on the idea.

"The blunt tool of banning diesel exports definitely doesn't work," Energy Secretary Chris Wright said at an event in New York, according to a Reuters report.

A White House official, responding to a question about Wright's remarks, told MarketWatch that Trump wants to see gasoline prices fall and is evaluating all the options.

Bespoke Investment Group also noted that a ban would plausibly lead to a reduction in global diesel supplies and in turn hurt profits at refining companies.

The group said that a consequence of the ban could be refineries on the U.S. Gulf Coast shuttering due to a lack of adequate storage capacity.

"In other words, the ban would likely reduce global diesel supplies in aggregate, hurting refiner profits," it said.

The research firm pointed out that a diesel ban would particularly affect New England, where Canada currently sources nearly half of the diesel consumed. An export ban could potentially lead to Canada selling diesel at an even higher price to other countries.

Ipek Ozkardeskaya, a senior analyst at Swissquote, noted Wednesday that the U.S. currently stands as the world's top diesel exporter.

"If it restricts exports, global diesel prices could simply spike," she wrote. "And because U.S. refiners would lose part of their export market, they could simply produce less - eventually tightening the supply of other fuels at home."

Robert Schroeder contributed.

-Nora Redmond