WASHINGTON, Sept. 13 – During a rally outside the White House Tuesday with leaders of the Standing Rock Sioux tribe and other tribal nations, Sen. Bernie Sanders (I-Vt.) called on President Barack Obama to block construction of the Dakota Access oil pipeline.

“If there is one profound lesson that the Native American people have taught us, it is that all of us as human beings are part of nature,” Sanders said. “Our species will not survive if we continue to destroy nature, so today we stand united in saying ‘stop the pipeline, respect Native American rights and let us move forward to transform our energy system away from fossil fuels.’”

The Standing Rock Sioux tribe has challenged the Army Corps of Engineers’ decision to grant permits for the pipeline at more than 200 water crossings. Tribal leaders allege that the project violates several federal laws and will harm water supplies. The tribe also says ancient sites have been disturbed during construction.

But Energy Transfer Partners, which is building the pipeline, used a loophole in the Army Corps of Engineers’ approval process to fast-track construction and avoid the more rigorous environmental and public review normally required for a project like the Dakota Access oil pipeline.

Sanders asked the president to close the loophole and require the company to conduct a standard review of the environmental and cultural impacts of the pipeline.

The federal government on Friday ordered work to stop on one segment of the project in North Dakota and asked the Texas-based company building it to “voluntarily pause” construction in the areas where Standing Rock Sioux leaders say there are sacred artifacts. Despite the action, the company is continuing to build the pipeline.

Like the Keystone XL pipeline, the Dakota Access pipeline will transport some of the dirtiest fuel on the planet, carrying half a million barrels of fracked crude oil from the Bakken oil fields in North Dakota, through South Dakota, Iowa and Illinois. Completing the Dakota Access pipeline would have the same impact on the planet as putting 21.4 million new cars on the road or building 30 new coal plants, according to Oil Change International.

Sanders came out against the pipeline last month. “As a nation, our job is to break our addiction to fossil fuels, not increase our dependence on oil,” he said at the time. “I join with the Standing Rock Sioux tribe and the many tribal nations fighting this dangerous pipeline.”