The Pentagon on Friday said a group of US-trained Syrian rebels had handed over equipment and ammunition to Al-Qaeda's affiliate in the country, the Al-Nusra Front.

"Unfortunately, we learned late today that the NSF (New Syrian Forces) unit now says it did in fact provide six pick-up trucks and a portion of their ammunition to a suspected Al-Nusra Front," Pentagon spokesman Jeff Davis said.

The startling admission contrasted with earlier Pentagon denials of reports that some fighters had either defected or handed over weapons.