Turkey's recent incursion into Syria to strike DAESH positions is an "indication of important progress" in securing the Turkish-Syrian border, the White House said Wednesday.

"Our NATO allies in Turkey have made valuable contributions to the counter-ISIL [DAESH] campaign, and this is just the latest example of it," spokesman Josh Earnest told reporters.

Earnest acknowledged that "tension between Turks and Kurdish forces" in Syria has "been simmering for a long time," but said the U.S. would continue its support for "unified forces" fighting DAESH in Syria.

Those forces include the People's Protection Units (YPG) that Turkey considers to be the Syrian branch of the PKK. Turkey, the U.S. and European Union consider the PKK a terrorist group, but Washington has refrained from listing the YPG similarly.

The YPG is the primary force within the U.S.-backed Syrian Democratic Forces, which has been supported by coalition airstrikes and special operators in their fight against DAESH.

"The fact is there have been diverse forces inside of Syria that, yes, that include some Kurds, but also are Arabs and Turkmen and others who have been an effective fighting force against ISIL and have been responsible for significant gains on the ground inside of Syria," he said, using an alternate name for DAESH.