U.S. Defense Secretary Jim Mattis says America will continue to provide weapons to Syrian Kurdish fighters after the battle to oust Islamic State militants from Raqqa, Syria.

Describing American reassurances to Turkey that the U.S. will take back weapons given to the Syrian Kurds after the IS group fight, Mattis says it depends on when or where the next mission is.

And he's also sounding a cautionary note when asked if all the weapons would be returned.

"We'll do what we can," the defense secretary told reporters traveling with him to Germany Tuesday.

Mattis' comments marked the first time he has spoken at length publicly about the U.S. pledge to recover the weapons provided to the Kurds.