Officials told CNN on Saturday that Colonel Gulmurod Khalimov, a former head of Tajikistan's special forces, took part in counterterrorism courses as part of a program sponsored by the State Department.
Blackwater Worldwide, which is now known as Academi and is based in McLean, Virginia, is the most notorious private security firm that had operated in Iraq and Afghanistan.
In his online video, Khalimov appears in black ISIL clothing with a sniper rifle and a bandolier of ammunition, claiming that he attended programs on American soil three times.
State Department spokeswoman Pooja Jhunjhunwala confirmed his claims.
"From 2003-2014 Colonel Khalimov participated in five counterterrorism training courses in the United States and in Tajikistan, through the Department of State's Diplomatic Security/Anti-Terrorism Assistance program," said Jhunjhunwala.
The program trains candidates from participating countries in the counterterrorism techniques, so they can fight terrorists.
The terrorist was trained in crisis response, tactical management of special events, tactical leadership training and other related issues, according to a State Department official.
Khalimov says in the video that what he witnessed during his training in the US turned him against Washington.
"Listen, you American pigs: I've been to America three times. I saw how you train soldiers to kill Muslims," he says in Russian. "You taught your soldiers how to surround and attack, in order to exterminate Islam and Muslims."
The ISIL terrorists, who were initially trained by the CIA in Jordan in 2012 to destabilize the Syrian government, now control large parts of Iraq and Syria.
Since last year, the US and some of its allies have been carrying out airstrikes against ISIL inside Iraq and Syria.
On February 19, the United States and Turkey inked an agreement to train and arm what they call "moderate" terrorist in Syria.
The Pentagon has deployed hundreds of Special Forces to the Middle East to train "moderate” terrorists to fight ISIL terrorists.