Secretary of Defense Mark Esper told reporters Monday that the U.S. would not be withdrawing troops from Iraq, despite a letter that surfaced earlier in the day suggesting otherwise.

According to reports by Reuters, the United States military wrote a letter to Iraqi officials -- just one day after Iraqi lawmakers approved a resolution calling to expel U.S. troops from the country -- telling them the U.S. would pull troops from the region and work on repositioning forces in the coming weeks.

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Esper, who said he had not seen the letter but noted that it is unsigned, said the contents are not consistent with current U.S. policy.

"There has been no decision to leave Iraq. Period," Esper said.

The confusion over withdrawing troops comes as tensions in the Middle East continue to rise in the days following the death of Iranian Gen. Qassem Soleimani who was killed in a U.S.-led airstrike on Thursday.

President Trump threatened to slap Iraq with heavy sanctions if U.S. troops -- who were sent there more than four years ago to aid in the fight against the Islamic State terror group -- were ousted from their posts.

"Bottom line. This was a mistake," Gen. Mark Milley, chairman of the Joint Chiefs of Staff, told reporters. "This was an honest mistake."

Milley called the letter “poorly worded” and said it “implies withdrawal. That’s not what’s happening.”

He clarified that there would be more U.S. troops moving around by helicopter as force protection increases inside Iraq, particularly in the heavily fortified Green Zone, which has been bombarded with rocket attacks over the past three days.

Milley also added that the U.S. military will be "bringing people in from Kuwait,” to add to the nearly 5,000 U.S. troops already on the ground.

“It was a draft, unsigned letter because we are moving forces around and we have increased helicopter movement in Iraq,” Milley said, adding that unsigned draft letters are often circulated in Washington, repeating that he thought this was an “honest mistake.”

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“It should not have been sent,” he said. “I walked down here intentionally in order to get control of that because that can have second- and third-order effects in a lot of directions in very dynamic situations.

“I don’t want to be misunderstood,” Milley added.

Fox News' Lucas Tomlinson contributed to this report.