Responding to a reporter’s question at the White House, Trump said he would be taking the step, with the suspension to remain in place “till it’s appropriate.”

“It’s a small percentage, but you know it’s still money,” he said.

US federal taxes on gasoline amount to 18.4 cents per gallon on gasoline and 24.4 cents per gallon for diesel, according to the US Energy Information Administration (EIA).

Suspending the tax would require an act of Congress, where Trump’s Republican party holds a razor-thin majority in both houses.

Trump ally Senator Josh Hawley said he would introduce legislation to do so on Monday. In the House, Republican Anna Paulina Luna made a similar pledge to introduce a bill “this week.”

US fuel prices have skyrocketed since Trump launched the war on Iran, with gasoline and diesel both up about 50 percent since late February.

Iran’s retaliatory action has included virtually closing the key Strait of Hormuz, through which about a fifth of the world’s oil and natural gas passes.

On Monday, the average price of a gallon of regular gasoline in the United States was $4.52, with diesel at $5.64, according to the AAA motor club.

Suspending the federal fuel tax would bring those prices down by about four percent.

State taxes on fuel, which average 32.61 cents per gallon for gasoline and 34.76 cents for diesel according to the EIA, would be unaffected by the move.