The US is removing four patriot missile batteries from Saudi Arabia as part of a rotation of its military assets in the region, officials said on Thursday.
The Pentagon said it would maintain “robust” capabilities in the region to counter any threat from Iran.
US Department of Defence spokesman Cmdr Sean Robertson told The National on Thursday that the US would move and circulate assets from Saudi Arabia.
"As part of the Department’s global force management processes, DoD routinely circulates troops and assets to address emerging threats and maintain readiness," Cmdr Robertson said.
But the troop rotations will not mean the US will have less ability to counter the threat from Iran, he said.
"The Department maintains robust in-theatre capabilities, including air defence, to address any Iran-related contingencies as needed," Cmdr Robertson said.
"We also maintain the capability to augment these forces on short notice.
"The Department of Defence continues to work with the international community and Saudi Armed Forces to strengthen regional air defence capabilities."
He stressed that the US-Saudi defence partnership was long-standing.
Saudi King Salman and US President Donald Trump reasserted their commitment to jointly ensure regional security in a phone call on Friday.
Mr Trump "stressed the US commitment to protect its interests as well as the security of its allies in the region, and its determination to confront any act that may destabilise the region", and reiterated US support for reaching a political solution in Yemen, the Saudi Press Agency reported.
The powerful Patriot missile batteries, sent to the region after missile and drone attacks on Saudi oil facilities last year, are due to be pulled out along with the 300 personnel who operate and protect them.
The Wall Street Journal earlier reported the US was "removing four Patriot missile batteries from Saudi Arabia along with dozens of military personnel".
It said the move marked "the end, for now, of a large-scale military build-up to counter Iran.”
Two US jet fighter squadrons have already left the region, the paper said.
“Well, I don’t want to talk about it but we’re doing some things,” President Donald Trump said on Thursday when asked about the decision to remove the Patriot batteries. “We’re making a lot of moves, in the Middle East and elsewhere. We’re doing a lot of things all over the world militarily.”
Late last year the Pentagon sent about 3,000 extra troops, fighter jets and other hardware, along with the air defence missile systems after the attack on oil installations and rise in tension in the Gulf.
The US also expanded its naval presence in the region.
The aim was to add to the kingdom's air and missile defence against possible rocket attacks from Iran.
In February, Greece said it would send some of its Patriot missiles to Saudi Arabia, in a programme arranged by the US, Britain and France.
Last week, Reuters reported that Mr Trump pressed Saudi Arabia to end its oil price war with Russia in April and threatened to withdraw US troops.
Mr Trump spoke with Russian President Vladimir Putin on Thursday.