A United Nations human rights official criticized the U.S. government’s handling of the Dakota Access pipeline project in a special report on Friday, saying it disregard treaties and ignored the interests of the Standing Rock Sioux Tribe.

Victoria Tauli-Corpuz, a U.N. special rapporteur examining issues related to Native American tribes in the United States, said in an interview that she was struck by the ineffective communication between tribes and federal and local governments across the country, particularly when it came to development and energy projects on or adjacent to Indian reservations. In her report, she said the federal government has shown a “lack of good faith involvement” of Native tribes in reviewing such projects.

While she acknowledged that there has been progress in the relationship between the federal government and tribal governments, Tauli-Corpuz said there has been widespread failure to adequately communicate and consult with indigenous peoples on issues “affecting their land, territory and resources.”

Tauli-Corpuz concluded her 10-day mission to the United States on Friday in Washington where she delivered a preliminary report on her visit to State Department officials. The trip took her to meetings with tribes, politicians and government officials in New Mexico, Arizona and Colorado. She also traveled to North Dakota, where she visited the Standing Rock Sioux Reservation, site of a year-long protest by Indians and environmentalists against the Dakota Access pipeline project.

The Standing Rock Sioux tribe has opposed the pipeline because it crosses the Missouri River a mile north of their reservation and, they say, poses a threat to their drinking water. The tribe has argued that it was not adequately consulted about the pipeline route – which it says crosses sacred burial grounds – and not given a chance to participate meaningfully in discussions about the project with the Army Corps of Engineers and other federal government representatives.

In an interview Thursday, Tauli-Corpuz said she was invited to the Standing Rock Sioux reservation by its chairman, David Archambault II, whom she met when he visited the U.N. in Geneva last year to speak about the tribe’s plight.

“In a show of disregard for treaties and the federal trust responsibility, the Army Corps approved a draft environmental assessment regarding the pipeline that ignored the interests of the tribe,” she wrote in her report. “Maps in the draft environmental assessment omitted the reservation, and the draft made no mention of proximity to the reservation or the fact that the pipeline would cross historic treaty lands of a number of tribal nations. In doing so, the draft environmental assessment treated the tribe’s interests as non-existent, demonstrating the flawed current process.”

According to Tauli-Corpuz, the experience of the Standing Rock Sioux tribe is shared by many other indigenous communities in the United States. She wrote, “From my conversations with people throughout Indian Country, I have learned that many of the complex issues that Native Americans face in the energy development context today are rooted in a long history of land and resource dispossession.”

She urged the government “to undertake meaningful consultations with the indigenous people before any project is brought to their communities.”

Tauli-Corpuz will soon return to Geneva and put together a full report that will contain findings, observations and recommendations that she will present at a September session of the U.N.’s Human Rights Council.

“I hope that the United States government will at least look at the report and take into account the recommendations that I have done and see how they can implement them,” she said. “And I hope that the indigenous people will also use the recommendations to push the government to implement them.”