"We're going to take off the gas tax for a period of time, and when gas goes down, we'll let it phase back in," Trump told CBS News.

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 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).

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.

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