US government officials are now reportedly promising to temporarily halt construction of the pipeline on federally owned land, which makes up a significant chunk of the land on which the pipeline would be built. The Obama administration said it would not authorize construction on land at Lake Oahe, a focal point of protests.

The move came on the heels of a ruling by federal judge, James E. Boasberg, in Washington DC, who earlier in the day rejected the Standing Rock Sioux tribe's appeal to halt construction of the Dakota Access oil pipeline. Boasberg said in a ruling that the decision by the US Army Corps of Engineers to fast-track the pipeline project was not illegal.

After Boasberg's ruling, tribal leaders reportedly filed a notice of appeal on Friday.

'Historic day'

Opposition to the pipeline has drawn support from 200 Native American tribes, as well as from activists and celebrities.

The Standing Rock Sioux, whose tribal lands are a half-mile (around 800 meters) south of the proposed route, say the pipeline would desecrate sacred burial and prayer sites, and could leak oil into the Missouri and Cannon Ball rivers, on which the tribe relies for water.

On Friday, the tribe called the intervention by the Obama administration "stunning," saying it set the stage for nationwide reform.

"Our hearts are full, this an historic day for the Standing Rock Sioux tribe and for tribes across the nation," said tribal chairman Dave Archambault II. "Our voices have been heard." Thousands of people have protested the proposed pipeline, including Green Party Presidential candidate Jill Stein.

Business wrath

Pipeline supporters, however, weren't so impressed.

"Should the administration ultimately stop this construction, it would set a horrific precedent," said the Midwest Alliance for Infrastructure Now in a statement. "We hope and trust that the government will base its final decision on sound science and engineering."

Dakota Access, a subsidiary of Energy Transfer Partners that is building the pipeline, declined to comment. The government has also called on Dakota Access to halt work on other land. As of late Friday, the company had not said whether it would comply.

When fully connected to existing lines, the 1,100-mile (1,770 km) Dakota Access pipeline would be the first to carry crude oil from the Bakken shale, a vast oil formation in North Dakota, Montana and parts of Canada, directly to the US Gulf.

jbh/cmk (Reuters, AP)