WASHINGTON: The United States deployed two B-52 long-range bombers over the Gulf Thursday in a show of force directed at Iran just as Washington moves to cut its ground-level military presence in the region.

The two bombers took off at short notice from Barksdale Air Force Base in Louisiana for the non-stop, 36-hour mission to cross Europe and then the Arabian Peninsula to the Gulf, looping near Qatar while keeping a "safe distance" from Iran's coastline, US defence officials said.

The mission, the second such in two months, "was designed to underscore the US military's commitment to its regional partners, while also validating the ability to rapidly deploy combat power anywhere in the world," according to US Central Command commander General Frank McKenzie.

While McKenzie did not name Iran as the focus of the mission, the US has used shows of force in the air and on the sea to deter Tehran from "malign behaviour" toward US forces and allies in the Gulf.

"Potential adversaries should understand that no nation on earth is more ready and capable of rapidly deploying additional combat power in the face of any aggression," said McKenzie.

The flight was coordinated with US allies, and aircraft from Saudi Arabia, Bahrain and Qatar flew with the bombers as they traversed the airspace, according to a US defense official.