The Pentagon said Friday that "several hundred" U.S. troops would receive orders in coming weeks to deploy to the Middle East to begin training moderate Syrian rebels.
Some deployment orders could come as early as next week, and troops could begin to deploy within the next four to six weeks, said Pentagon press secretary Rear Adm. John Kirby.
The expected number of trainers — a mix of special operations forces and conventional forces, will be 400, according to Defense One.
However, a similar number of troops to support the trainers could also deploy, Kirby said, including those to protect the trainers.
He said the total number "could approach 1,000," and "might even exceed that."
However, it was too early to pinpoint the number, or where the U.S. troops would be coming from, Kirby said.
The $500 million plan to train and equip 5,400 Syrian rebels is a key part of the administration's plan to defeat and degrade the Islamic State in Iraq and Syria (ISIS).
The administration proposed the plan in June. Congress first approved it in September for three months, and in December, extended the program through 2016.
The purpose of the plan is to provide the moderate Syrian opposition with basic military skills necessary to train more opposition members in order to fight ISIS in Syria, as well as to bring about a "political solution" in Syria — where they are also fighting the Bashar Assad regime.
Skeptics of the plan doubt whether the U.S. can identify trainees who are not affiliated with Islamic extremists, due to the confusing and shifting alliances on the ground.
Kirby said the U.S. is working with moderate opposition leaders to identify moderate groups who could be recruited for the program.
"There's going to be a significant vetting program in place," he said, acknowledging that some trainees could pose a risk to U.S. forces.
In 2012, there was a spate of attacks by Afghan troops on their U.S. and coalition trainers, known as "green on blue" attacks. While some of the Afghan troops acted out of anger, some attacks were by Taliban infiltrators or others sympathetic to the Taliban.
Kirby said no recruiting has begun yet, and that the training would not start before March. The rebels would be ready to fight by the end of the year, at the earliest.
Other coalition partners, including those hosting training sites, are expected to contribute trainers in the "hundreds," Kirby said.