WASHINGTON, United States (AFP) — United States (US) consumers saw some relief at the fuel pump on Thursday, as the average price of a gallon of regular gasoline fell below US$4 for the first time since March, according to the AAA motor club.

Global oil prices have tumbled after US President Donald Trump and Iranian counterpart Masoud Pezeshkian signed off on a deal to end their war and reopen the Strait of Hormuz to tanker and other shipping traffic.

The war sent energy prices surging, after Iran’s retaliatory actions included blocking the vital waterway, through which a fifth of the world’s oil and gas supplies normally pass.

US households have been battered by years of high prices, and the energy price shock has sent inflation surging to a three-year high.

The average price of a gallon of regular gasoline logged in at US$3.99 on Thursday, according to AAA. It remains 34 per cent higher than on the day before the war was launched.

On Wednesday, US Federal Reserve Chair Kevin Warsh vowed that the central bank would “deliver price stability”, with some policymakers indicating interest rate hikes were on the horizon.

The Fed has a long-term two per cent target for inflation, but price increases have remained above that level for more than five years.

In April, the Fed’s preferred gauge of inflation came in at 3.8 per cent, fuelled in part by surging energy prices.

Affordability is a key political issue as the United States gears up for midterm elections in November, with the Democratic Party seeking to wrest control of both houses of Congress from Trump’s Republicans.