The New York Times reported that some U.S. congressional Republicans, following an unprecedented increase in diesel prices, have called for a ban on exporting this fuel. According to the report, the Iran war and reduced global refining capacity have been the main factors behind the surge in prices.

The average diesel price in the United States reached $6.53 per gallon on Tuesday, compared with $3.69 a year earlier. Donald Trump, the U.S. president, also said that his administration is considering a ban on diesel exports to reduce fuel costs for farmers, truck drivers, and businesses.

The United States is the world’s largest supplier of diesel and provides about 20% of the eight million barrels of diesel that are traded daily by sea.

The American Petroleum Institute warned that export restrictions could encourage refineries to cut production and intensify the global shortage. Mike Sommers, the head of the institute, said that limiting U.S. energy exports “will only make the problem worse.” Jim Mechals, head of oil trading analysis at Wood Mackenzie, also said that a temporary ban on exports is possible, but it will not necessarily lead to a rapid drop in diesel prices.