Native American and environmental activists have vowed to block a planned crude oil pipeline, hinting at a standoff in Oklahoma reminiscent to the monthslong Dakota Access Pipeline protest.

Once built, the $900 million Diamond Pipeline will carry sweet crude oil from a national transport hub in Cushing eastward toward Tennessee. Opponents said the project was crafted without input by tribes and might disturb unidentified graves of ancestors who were marched to Oklahoma along the Trail of Tears.

Organizer Mekasi Camp Horinek declined to say where the protesters would set up along the pipeline's route but warned that actions could begin soon.

“There definitely will be an encampment that's going to come here to Oklahoma in the near future where we can call on our allies, our brothers and sisters, the connections we made during that fight at Standing Rock,” said Horinek, state director for Bold Oklahoma.