Small numbers of U.S. special operations forces for the first time are accompanying Turkish government forces and their Syrian opposition partners fighting Islamic State militants inside Syria, military and administration officials said Friday.

The move follows a period of U.S. tensions with Turkey, including U.S. criticism of clashes last month between Turkish and Syrian Kurdish forces in northern Syria. Turkey is a NATO ally of Washington's, but it has been angered by U.S. support for the Kurdish YPG militia, which has been the most effective U.S. partner in fighting the Islamic State in Syria.

A Pentagon spokesman, Navy Capt. Jeff Davis, said the Americans are advising and providing other assistance to Turkish troops who are clearing territory on the Syrian side of Turkey's border between the Syrian towns of Jarablus and Ar Rai.

"Access to the Turkey-Syria border region is strategically important to ISIL's operations in Syria and Iraq as well," Davis said, using a common acronym for the Islamic State.

"Denying ISIL access to this critical border cuts off critical supply routes in and out of Iraq and Syria and further isolates ISIL's so-called `capital' in Raqqa," said another Pentagon spokesman, Marine Maj. Adrian J.T. Rankine-Galloway.

White House spokesman Josh Earnest noted the U.S. has long pushed Turkey to enhance security along its border.

"We have been pleased to see the Turkish pursue this kind of decisive, strategically significant action that will aid our efforts," he said.

Davis said the Americans are providing the same training, advice and other assistance that U.S. forces have been providing to other Syrian opposition groups -- such as the Kurdish-led Syrian Democratic Forces -- fighting the Islamic State in northern Syria. This is the first time, however, that U.S. troops have performed this role alongside Turkish troops.

Davis did not say how many U.S. troops are working with the Turks, but others said it was approximately a few dozen. They are among 300 U.S. troops authorized by President Barack Obama to provide training, advice and assistance inside Syria as part of the broader military campaign against the Islamic State in Iraq and Syria.

Officials said not say how long the U.S. special operations troops will work with the Turks and their Syrian opposition partners, but it appeared likely they will help with Turkish-led operations aimed at clearing the towns of al-Bab and Dabiq, which are south and southwest of Ar Rai and are under Islamic State control.