Story highlights Anti-ISIS coalition spokesman says it's "unauthorized and inappropriate" for U.S. forces to wear YPG patches

A news agency published photos it says are of U.S. special operations forces operating near the front lines north of Raqaa

Washington (CNN) The Pentagon has pushed back on assertions that U.S. special operations forces were fighting ISIS fighters on the front lines alongside the Syrian forces they are advising.

Photos: Photos: Agence France-Presse published photos on May 26 the news agency says are of U.S. special operations forces operating near the frontlines north of Raqqa, Syria. Here, armed men in uniform identified by Syrian Democratic Forces as U.S. special operations forces walk in the village of Fatisah in the northern Syrian province of Raqqa on May 25, 2016. Hide Caption 1 of 5 Photos: The Pentagon pushed back against the idea that the Americans were fighting. Here, the U.S. special operations forces ride in the back of a pickup truck in the village of Fatisah in the northern Syrian province of Raqqa on May 25, 2016. Hide Caption 2 of 5 Photos: In the back of a pickup truck in the village of Fatisah in the northern Syrian province of Raqqa, armed men in uniform identified by Syrian Democratic Forces as U.S. special operations forces ride on May 25, 2016. Hide Caption 3 of 5 Photos: Armed men in uniform identified by Syrian Democratic forces as U.S. special operations forces ride in the back of a pickup truck in the village of Fatisah in the northern Syrian province of Raqqa on May 25, 2016. The Syrian Democratic Forces (SDF) announced on May 24 its push for IS territory north of Raqa city. Hide Caption 4 of 5 Photos: Armed men in uniform (R) identified by Syrian Democratic forces as U.S. special operations forces walk in the village of Fatisah in the northern Syrian province of Raqqa on May 25, 2016. U.S.-backed Syrian fighters and Iraqi forces pressed twin assaults against the Islamic State group, in two of the most important ground offensives yet against the jihadists. Hide Caption 5 of 5

Agence France-Presse published photos Thursday that the news agency says are U.S. special operations forces operating near the front lines north of Raqaa, ISIS's self-declared capital, as they conduct their advise-and-assist mission of the Syrian Democratic Forces, or SDF, that the United States is assisting in the battle to defeat ISIS.

"Our forces in Iraq and Syria, their instructions, their mission, is clear that they are not at that leading edge," Pentagon press secretary Peter Cook told reporters Thursday. "They're able to defend themselves, but they have to be in a position to be able to provide the kind of advice and assistance needed to help these forces, these local forces, succeed."

Since the beginning of U.S. military involvement in Iraq and Syria against ISIS, U.S. officials have maintained that U.S. forces on the ground are only there to advise and assist local forces in their fight against ISIS, and are prohibited under the rules of engagement to conduct offensive military operations against ISIS.

Despite the apparent closeness to kinetic action in the photos, Pentagon officials maintain that rule of engagement holds true in Syria, even though there is no fixed position inside Syria from where U.S. forces cannot move forward from.

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