The Army Corps of Engineers said it won't forcibly remove protesters from blocking the route of the contentious Dakota Access oil pipeline in North Dakota, but it wants all activists off the land by next Monday or risk federal prosecution.

The Army Corps said Sunday it "is seeking a peaceful and orderly transition to a safer location and has no plans for forcible removal." But it warned that those who remain may be cited and fined under federal and state laws.

The agency said the removal of the protest camp from federal land "will reduce the risk of harm to people in the encampments caused [by] the harsh North Dakota winter conditions."

The Army Corps announced Friday that it would close federally managed lands near the oil pipeline's route, which include the main camp site where Indian tribes and activists have been staging protests to block construction of the project.

The Army Corps made the decision to close the area after clashes between activists and police rose to new heights before Thanksgiving.

A number of activist and tribal groups protesting the 1,200-mile long, $3.8 billion crude oil pipeline decried the Army Corps decision on Sunday, calling it a "slap in the face," according to Tara Houska, national campaign director for Honor the Earth, in issuing a joint statement with other groups. "Indigenous peoples on treaty lands are not trespassers," she said.

The Army Corps said Sunday that it had issued the land closure order "after coordination with tribal leaders involved in the ongoing protest of the Dakota Access Pipeline on which some of the land is currently leased to a local rancher for grazing."

The agency sent letters to the head of the Standing Rock Sioux Tribe and others Friday warning them that federal land managed by the Army Corps north of the Cannonball River will be closed to the public beginning Dec. 5. The Sioux are leading the protest against the pipeline over concerns that it would threaten the tribe's drinking water supply and mar sacred lands.