Several hundred protesters from at least 100 Native American tribes have joined a weeks-long protest to support the Standing Rock Sioux Tribe in its bid to stop construction of the Dakota Access oil pipeline.

The tribe argues that the $3.8 billion (3.4 billion euros) pipeline, which will pass through Iowa, Illinois, North Dakota and South Dakota, threatens its sacred sites and drinking water. The Sioux group also says it was not properly consulted before construction began on the pipeline.

As the protest gained momentum, the tribes have been joined by environmental groups concerned over the impact of fossil fuels on climate change. Several groups have also expressed serious concerns over the environmental impact of the pipeline's construction and ensuing usage, as it threatens numerous ecosystems along its route, thereby impacting groundwater safety and crop production, among other issues. Several celebrities have joined in the demonstrations and nearly 30 protesters have been arrested in recent weeks.

The Standing Rock Sioux tribe is seeking an injunction stopping construction of the pipeline. For the moment, construction near the reservation straddling the North and South Dakota border has been put on hold.

Over 1000 activists, including Susan Sarandon, rallied in Washington in solidarity with the Standing Rock Sioux.

A federal judge is set to rule by September 9 whether to order a halt to construction on a section of the pipeline near the Standing Rock Sioux Tribal Reservation.

Separately, last Thursday the Iowa Utilities Board denied a request by 14 landowners to halt construction of the pipeline while a court examines a lawsuit.

The lawsuit challenges the board's authority to approve eminent domain for a privately owned pipeline. A key question to be answered by the court is whether a private entity can use state power to can take private property from citizens for the private profit of the entity.

Once completed, the 1,170-mile (1,880-km) pipeline will bring nearly a half a million barrels a day of Bakken crude from shale deposits in North Dakota to Illinois. From there, existing pipelines will carry the crude to refineries on the Gulf Coast.

Developers say the pipeline will save money and time in transporting crude. They also argue pipelines are more environmentally friendly than moving crude by rail.

The developers, Energy Transfer Partners, have already received nearly all the state and federal licenses for the pipeline and hope to complete it by the end of the year.

Sections of the pipeline are already completed in North Dakota and Iowa, and preparatory work is underway along the pipeline path.

However, tribal groups, environmentalists and landowners are expected to put forward a lengthy legal battle that could tie up work on the project.

cw/kl (AP, Reuters)