The U.S. military informed its counterparts in Baghdad on Monday it was preparing for "movement out of Iraq," a day after the Iraqi parliament urged the government oust foreign troops, according to media reports that got copies of the letter.

However Defense Secretary Mark Esper says the United States has made "no decision" about withdrawing troops from Iraq amid heightened tensions with neighboring Iran.

The head of the U.S. military's Task Force Iraq, Brigadier General William Seely, had sent a letter to the head of Iraq's joint operations command, a copy of which was seen by AFP.

The letter said troops would "be repositioning forces over the course of the coming days and weeks to prepare for onward movement."

A U.S. defense official and an Iraqi defense official confirmed the letter was real and had been delivered.

However Esper spoke to reporters after the letter circulated online saying "There's been no decision whatsoever to leave Iraq."

With input from AFP and AP.