General Jonathan Vance, chief of defense staff, announced the "operational pause" in a letter posted on Twitter to families of deployed military personnel.

"Over the coming days, and as a result of Coalition and NATO planning, some of our people will be moved temporarily from Iraq to Kuwait.

"Simply put, we are doing this to ensure their safety and security," he wrote.

The move comes amid heightened concerns over possible Iranian retaliation for the killing of a top Iranian commander, Qasem Soleimani, on Friday on orders of US President Donald Trump.

NATO, which suspended its training mission in Iraq after the killing, said earlier Tuesday it also was temporarily "repositioning" some personnel to locations inside and outside Iraq.

Several other countries, including Germany and Romania, also announced plans to move their forces. France, for its part, said it had no intention to withdraw its troops from Iraq.

"The situation in Iraq is complex and it is best to pause our work there in order to fully concentrate our attention and efforts toward the safety and security of our personnel while the situation develops," Vance said.