The U.S. military moved refueling tankers out of Royal Air Force (RAF) Mildenhall in England on Monday after a threat from Iran, The Wall Street Journal reported.
It is the second British air base evacuated in recent weeks, following the withdrawal of U.S. bombers from RAF Fairford over a suspected Iran-linked plot.
Two U.S. refueling tankers using Mildenhall diverted to Germany that morning, and several other tankers at the base moved to Germany and other locations later in the day, according to flight-tracking data and an official cited by the WSJ.
U.S. officials are still discussing whether the threat to the base is imminent or more general, the newspaper reported, citing people familiar with the matter.
The U.S. raised the security posture at RAF Mildenhall and RAF Lakenheath, both used by the U.S. military, to FPCON Charlie, a U.S. official told the WSJ.
The level applies when an incident occurs or intelligence indicates that some form of terrorist action or targeting against personnel or facilities is likely.
The War Zone first reported the change.
"We do not routinely comment on the activity of other nations. Aircraft and other assets move regularly according to operational requirements," a British Defense Ministry spokesperson told Reuters.
A U.S. Air Force spokesperson declined to give details to WSJ, saying aircraft rotate between installations for a variety of reasons.
The White House referred questions to the Pentagon.
The "Gang of Eight," Congress’ top political and intelligence leaders, received a briefing Monday on Iran’s threats, a person familiar with the meeting told the WSJ.
Tehran has said its retaliation for any U.S. attack would expand beyond the Middle East.
Director of National Intelligence Jay Clayton said in October that Iran was in "advanced stages" of planning to target U.S. personnel in the Middle East, prompting the evacuation of diplomats from regional posts.
"We’ve addressed it by moving people away from the threat," Secretary of State Marco Rubio said Monday.
Last month, the Pentagon sent B-1 bombers back to the U.S. from RAF Fairford, which had been used for strikes on Iran, amid concerns over an alleged Iran-backed plot to kill American pilots and target aircraft with drones.
Five British men were arrested outside the base in September.
The move came as Trump wrote on social media that a return to war with Iran was "unlikely."
"At this point, taking military action doesn’t seem to be a very necessary thing," he told reporters at the White House, citing progress in negotiations and Middle Eastern allies’ preference for maintaining the blockade.
"Should there be any change with respect to developments in the Middle East, the United States of America is ‘locked and loaded’ and ready to go," Trump wrote, as concerns over threats to RAF Mildenhall persist.