The United States has started withdrawing its troops from Syria, a U.S. official told the Associated Press on Friday.

Col. Sean Ryan, spokesperson for the coalition fighting the Islamic State, said that the United States has begun “the process of our deliberate withdrawal from Syria.”

“Out of concern for operational security, we will not discuss specific timelines, locations or troops movements,” he said in a statement.

The U.K.-based Syrian Observatory for Human Rights, which observes the conflict in Syria, said the withdrawal commenced on Thursday night. It said that a group of approximately 10 armored vehicles, along with some trucks, left the northeastern Syrian town of Rmeilan into Iraq.

A Trump administration official told CNN that “some cargo has already moved.”

This development comes as there has been some confusion over the American exit plan from Syria, a plan of action U.S. President Donald Trump announced unexpectedly last month.

Amid fears that Syria’s Kurds could be targeted by Turkey, U.S. Secretary of State Mike Pompeo and U.S. National Security Advisor John Bolton have reassured that the Kurds will be protected. Even Trump previously said, “We want to protect the Kurds, but I don’t want to be in Syria forever. It’s sand and it’s death.”

In Cairo on Thursday, Pompeo reiterated that the United States will continue airstrikes against ISIS and support regional forces, such as Israel, to stop Iran in Syria and other places.

Reportedly, troops will leave over four months, as opposed to an initial 30-day period, though Trump has said “I don’t know, somebody said four months, but I didn’t say that either.”