The B-52 bombers ordered by the White House to deploy to the Persian Gulf to counter unspecified threats from Iran are beginning to arrive at a major American air base in Qatar.

Images released by the U.S. Air Force show B-52H Stratofortress bombers arriving at Al Udeid Air Base in Qatar on Thursday. Others landed at an undisclosed location Wednesday.

The Air Force identified the aircraft as coming from the 20th Bomb Squadron of Barksdale Air Force Base in Louisiana.

On Sunday, the White House announced it would send the USS Abraham Lincoln aircraft carrier strike group and the bombers to counter Tehran.

On Wednesday, Iran announced it would begin backing away from its nuclear deal with world powers, a year after President Donald Trump pulled America from the accord.

The Defense Department sent several nuclear-capable B-52s to the region following 'recent and clear indications that Iranian and Iranian proxy forces were making preparations to possibly attack US forces'.

A B-52H Stratofortress assigned to the 20th Expeditionary Bomb Squadron is seen through night vision coming in for a landing at Al Udeid Air Base, Qatar Thursday

The B-52 bombers ordered by the White House to deploy to the Persian Gulf to counter unspecified threats from Iran are beginning to arrive at a major American air base in Qatar

'The deployment of the USS Abraham Lincoln Carrier Strike Group and a bomber task force are considered a prudent step in response to indications of heightened Iranian readiness to conduct offensive operations against US forces and our interests,' said acting Pentagon spokesman Charles Summers in a statement.

'We emphasize the White House statement that we do not seek war with the Iranian regime, but we will defend US personnel, our allies and our interests in the region.'

The deployment was first announced late Sunday by John Bolton, President Donald Trump's national security advisor, who said the move was 'a clear and unmistakable message to the Iranian regime that any attack on United States interests or on those of our allies will be met with unrelenting force.'

The US move comes in response to intelligence about a threat orchestrated by Iran, officials said, but details of the threat have not been disclosed.

Navy Captain Bill Urban, the spokesman for the US military's Central Command, which spans the Middle east, said the threat could be land-based or maritime.

He said the Lincoln strike group was already scheduled to head to the region on long-planned deployment but that its arrival in the Gulf has been accelerated due to the threat.

Images released by the U.S. Air Force show B-52H Stratofortress bombers arriving at Al Udeid Air Base in Qatar on Thursday. Others landed at an undisclosed location Wednesday

The White House announced it would send the USS Abraham Lincoln aircraft carrier strike group and the bombers to counter Tehran on Sunday

That led to the cancellation of a planned port visit by the Lincoln to Split, Croatia.

The multinational carrier group, including several ships, multiple types of aircraft, and 6,000 personnel, will be deployed 'where it will best be able to protect US forces and interests in the region and to deter any aggression'.

The deployment comes a year after Trump pulled the United States out of a multinational accord under which Tehran drastically scaled back its sensitive nuclear work.

Since then, the Trump administration has ramped up menacing rhetoric against Iran while tightening economic sanctions on the country.