The US Army has informed Congress that it will grant permission to complete the controversial Dakota Access Pipeline near tribal territory.
The notice comes a month after Donald Trump formally backed the project in one of his first acts as US president.
Thousands of predominantly Native American protesters have boycotted the $3.8bn (£3bn) pipeline’s construction in the state of North Dakota.
The Standing Rock Tribe vowed to fight the decision in court.
The 1,172 mile (1,886km), four-state project is almost finished except for a one-mile stretch under Lake Oahe in North Dakota, where demonstrators have set up protest encampments.
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