The US has pulled aircraft out of RAF Mildenhall, a British base, because of a threat from Iran, sources familiar with the matter said on Tuesday. Two air refuelling tankers normally based there were redirected to Germany on Monday morning.
Several other tankers had been moved earlier to Germany and elsewhere.
Senior US officials are still discussing what the threat to the base is. The US Air Force did not comment directly. In a written statement, it said American aircraft are regularly rotated between bases and operating sites for various reasons.
About a month earlier, the US pulled all 12 B-1 bombers out of another British base, RAF Fairford. That followed intelligence about an alleged Iran-backed terror plot against the base.
Reports at the time said the bombers were withdrawn quickly after commanders received information about a possible drone attack ordered by the Islamic Revolutionary Guard Corps.