Officials have blocked supplies reaching oil pipeline protesters in North Dakota.
Demonstrators have been voicing their concerns over plans to route a $3.8 billion Dakota Access Pipeline beneath a lake near the Standing Rock Sioux reservation and claim the proposals pose a threat to water resources and Native American sites.
State officials have threatened to use fines and a physical blockade to keep protesters from receiving portable bathrooms, food and building materials.
Maxine Herr, a spokeswoman for the Morton County Sheriff's Department, said the primary concern was public safety.
"The governor is more interested in public safety than setting up a road block and turning people away," Ms Herr said.
Officers said they will stop vehicles they believe are headed to the camp and inform drivers they could be fined up to $1,000.
The activists, who have been protesting for months, said state officials were “bullying” demonstrators and questioned the legality of the fines.
"It's bogus and I don't know about the legality of it," said Kandi Mossett, an organiser for Indigenous Environmental Network.
"We're not afraid. We're moving in and out of the camp at will. So people shouldn't be afraid of coming and supporting the water protectors. They've been bullying us since day one."
The demonstrators also claimed law enforcement have used excessive force and suggested local police have used water cannons and tear gas on the protesters.
