Photos have emerged of American special operations troops in Syria wearing uniform insignia affiliated with a Kurdish rebel group known as the YPG, whose connection to Turkish terrorists could could fuel tension between the U.S. and a key ally in the Islamic State fight.

The images were taken in a village about 40 miles north of the Islamic State group's self-declared capital of Raqqa, which is the target of a newly announced offensive being led by a disparate group of Kurdish and Arab fighters, and backed by American military advisers and air support. They highlight the complicated network of alliances the U.S. is trying to forge in Syria, and the ethnic and sectarian tensions that could tear apart this fragile coalition.

Speaking Thursday, a top Pentagon official said it's fairly common for Green Berets and other operators to wear allies' patches .

"Special operations forces, when they operate in certain areas, do what they can to, if you will, blend in with the community to enhance their own protection, their own security," said Pentagon spokesman Peter Cook .

Armed men in uniform identified by Syrian Democratic forces as US special operations forces ride in the back of a pickup truck in the village of Fatisah in the northern Syrian province of Raqa on May 25, 2016. US-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. The Syrian Democratic Forces (SDF), formed in October 2015, announced on May 24 its push for IS territory north of Raqa city, which is around 90 kilometres (55 miles) south of the Syrian-Turkish border and home to an estimated 300,000 people. The SDF is dominated by the Kurdish People's Protection Units (YPG) -- largely considered the most effective independent anti-IS force on the ground in Syria -- but it also includes Arab Muslim and Christian fighters. / AFP / DELIL SOULEIMAN (Photo credit should read DELIL SOULEIMAN/AFP/Getty Images)

The Pentagon says U.S. troops in Syria are conducting an advise-and-assist mission and are not serving in front-line combat. Here, one American commando can be seen wearing a uniform patch of a Kurdish rebel group.

Photo Credit: Delil Souleiman/AFP/Getty Images

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Taken by a photographer working for Agence France-Presse, the photos show a cadre of American troops in an unarmored Toyota pickup truck mounted with a grenade launcher. At least one bearded soldier is wearing both an American flag patch and also a green patch with a star signifying the Syrian Kurdish People’s Protection Forces, known as the YPG.

A rmy Col. Steve Warren, a spokesman for U.S forces in Iraq and Syria, called the patch a "sign of partnership."

.@MarcShlikoff US Special operators will often wear patched from their partner forces as a sign of #partnership #TalkOIR — OIR Spokesman (@OIRSpox) May 26, 2016

But the photos could cause diplomatic tension with Turkey, a NATO ally that opposes U.S. support for the YPG. Turkey considers the YPG militia akin to the Kurdistan Workers Party, known as the PKK, a Turkey-based group that has mounted terrorist attacks in Turkey.

Close-up of the Kurdish militia patch being worn by American commandos in Syria.

Photo Credit: Delil Souleiman/AFP/Getty Images

The patch is also significant because the United States' nominal ally in Syria is the Syrian Democratic Forces, a recently created umbrella group that U.S. defense officials insist includes Arabs as well as Kurds. Many Syria experts, however, say the vast majority of SDF fighters are Kurdish and that few Sunni Arabs are supporting the group.

There are currently 300 U.S. special forces troops authorized to be in Syria.

The photos have raised new questions about how close these U.S. troops are to front-line combat. Cook declined to say where those troops were, citing operational security.

"They are on an advise-and-assist mission with forces that are carrying out the fight against [Islamic State militants]; trying to lend their support to them; use their skill set and their capabilities to enhance the effectiveness of those forces," Cook said. "They are not at the front line ."

Armed men in uniform identified by Syrian Democratic forces as US special operations forces walk in the village of Fatisah in the northern Syrian province of Raqa on May 25, 2016. US-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. The Syrian Democratic Forces (SDF), formed in October 2015, announced on May 24 its push for IS territory north of Raqa city, which is around 90 kilometres (55 miles) south of the Syrian-Turkish border and home to an estimated 300,000 people. The SDF is dominated by the Kurdish People's Protection Units (YPG) -- largely considered the most effective independent anti-IS force on the ground in Syria -- but it also includes Arab Muslim and Christian fighters. / AFP / DELIL SOULEIMAN (Photo credit should read DELIL SOULEIMAN/AFP/Getty Images)

American commandos walk in the Syrian village of Fatisah, north of Raqqa, on May 25, 2016.

Photo Credit: Delil Souleiman/AFP/Getty Images