*Earlier reports said US has notified Baghdad of its troop withdrawal
US Defence Secretary Mark Esper denied on Monday that US forces would pull out of Iraq, after a US general's letter told the Iraqi government that troops were preparing to depart "in due deference to the sovereignty" of the country.
"There is no decision whatsoever to leave Iraq... There has been no decision made to leave Iraq. Period," Esper said, one day after the Iraqi parliament voted in favour of ordering the US military out.
"That letter is inconsistent with where we are right now," Esper added.
Explaining the confusion, Pentagon Joint Chiefs Chairman Mark Milley said the official US letter informing Iraq that American troops would begin pulling out was "genuine" but not intended to be sent at this time.
"This was a mistake from McKenzie," Milley told reporters, referring to US Central Command commander General Frank McKenzie. "It shouldn't have been sent," Milley said.
According to earlier reports, the United States-led military coalition against Islamic State said that it was pulling out of Iraq and would be repositioning forces over the next few days and weeks.
"Sir, in deference to the sovereignty of the Republic of Iraq, and as requested by the Iraqi Parliament and the Prime Minister, CJTF-OIR will be repositioning forces over the course of the coming days and weeks to prepare for onward movement," read a letter from United States Marine Corps Brigadier General William H Seely III, the commanding general of Task Force Iraq to his Iraqi counterpart.
The authenticity of the letter, which was addressed to the Iraqi defence ministry's Combined Joint Operations Baghdad, was confirmed to Reuters independently by an Iraqi military source.
"We respect your sovereign decision to order our departure," it said.
"In order to conduct this task, Coalition Forces are required to take certain measures to ensure that the movement out of Iraq is conducted in a safe and efficient manner," said the letter, dated June 6.
As the letter was signed by a US official, it was not immediately clear whether it applied to forces from the 76 countries which make up the international coalition.
A US defence official and an Iraqi defence official confirmed the letter was real and had been delivered.
It said helicopters would be travelling in and around the Green Zone as part of the preparations.
AFP could hear helicopters flying low over Baghdad throughout Monday night.
Some 5,200 US soldiers are stationed across Iraqi bases to support local troops preventing a resurgence of the Islamic State group.
They make up the bulk of the broader coalition, invited by the Iraqi government in 2014 to help combat the jihadists.
On Sunday, Iraq's parliament voted in favour of rescinding that invitation and ousting all foreign troops.
It came in reaction to a US precision drone strike on Baghdad that killed Iranian general Qasem Soleimani and top Iraqi commander Abu Mahdi al-Muhandis, among others.
on Monday, Iraqi premier Adel Abdel Mahdi met with the US Ambassador Matthew Tueller, telling him it was "necessary to work together to withdraw foreign forces from Iraq".