A US B-52 bomber flew over the Middle East Wednesday in a show of force by President Joe Biden's new administration as it girds for a challenging relationship with Iran, the Pentagon said.

The nuclear-capable B-52H Stratofortresss flew the round-trip mission from Barksdale Air Force Base in Louisiana, accompanied at different times by US fighter jets and refuelling tankers, and, at one point, by Royal Saudi Arabian Air Force F-15 fighters.

It was the third such mission this year, the first two carried out by the previous administration of Donald Trump to maintain a threat presence against Iran.

While Biden, who became president on January 20, has signalled a readiness to thaw relations with Tehran, the new mission showed that US strategic policy has not changed.

"This long-range, short-duration defensive mission was intended to demonstrate the US military’s ability to deploy airpower anywhere in the world to deter potential aggression and showcase the US commitment to regional security," the US Central Command said in a statement.

"Centcom is committed to partner security and preserving regional stability," it said.