"Russian organizers will hold a Koktebel Jazz Party August 28-30 in Crimea. Crimea remains Ukrainian territory and this event is being conducted without the permission of the Government of Ukraine," the embassy said.
The embassy reminded US citizens of "broad sanctions on activity in Crimea."
"US citizens are prohibited by law from providing services to the territory of Crimea," the embassy said.
The Koktebel Jazz Party international music festival will be held in Koktebel, a popular resort in Crimea’s east, for the 13th time. The festival’s box office revenues will be spent on the development of Crimean cultural sites, organisers said.