The U.S. military is preparing to leave Iraq, according to a letter posted on Twitter that a defense official confirmed to Task & Purpose is authentic.

Written by Marine Brig. Gen. William Seely III, the unsigned letter to the Iraqi defense ministry says the U.S. military will be “repositioning forces over the course of the coming days and weeks to prepare for onward movement.”

“During this time, there will be an increase in helicopter travel in and around the International Zone (IZ) of Baghdad,” Seely wrote in the Jan. 6 letter. “The increase traffic will include CH-47, UH-60, and AH-64 security escort helicopters.”

Coalition forces will conduct the withdrawal at night to avoid creating the appearance that the U.S. military is bringing more troops into the Green Zone, Seely wrote in the letter.

On Sunday, Iraqi lawmakers voted to expel all American troops from Iraq in response to the U.S. airstrike that killed Qasem Soleimani, former head of the Islamic Revolutionary Guard Corps. The decision would have to be approved by the government once Iraq agrees on a new prime minister.

“We respect your sovereign decision to order our departure,” Seely wrote in the letter.

This is a breaking news story and it will be updated as more information becomes available.