Congresswoman Tulsi Gabbard, the Hawaii Democrat who served two tours of duty in the Middle East, and who continues to serve as a major in the Army National Guard, will join thousands of veterans next week as they arrive to support Native Americans who are seeking to block construction of an oil pipeline near North Dakota’s Standing Rock Sioux Reservation.

“If my participation in this protest helps send one message, it is this: We must protect our fragile water resources for current and future generations,” says Gabbard, who since her youth has been an environmental activist.

The congresswoman will be part of a December 4-7 “Veterans Stand With Standing Rock” mobilization that proposes to bring military veterans from across the country to North Dakota at the same time that state officials are stepping up efforts to remove pipeline foes from the camp they have organized as part of their Water Protectors movement.

The objections raised by the Standing Rock Sioux tribe and its allies to the Dakota Access Pipeline have captured the attention of indigenous activists and climate-change campaigners from across the country and around the world; and the corporate interests that are seeking to complete the pipeline have made little secret of their frustration with the protests. Now state officials are telling members of the tribe that they must leave. North Dakota Governor Jack Dalrymple has issued an evacuation order for the sprawling campsite where Native Americans from many tribes have gathered to protect sacred lands and the region’s water supply. The Army Corps of Engineers has announced plans to take steps on December 5 to close off access to the camp. But tribal leaders say they intend to remain in place at what has been described as “the largest gathering of Indian people in North America in the past century.”

More than 2,000 veterans have indicated that they will join a nonviolent intervention to protect and support the foes of the pipeline from what organizers of the mobilization describe as “assault and intimidation at the hands of the militarized police force.” Authorities have used mass arrests, rubber bullets, pepper spray, and water cannons to deter protests. They have also arrested journalists and documentary filmmakers seeking to report from the scene.

Gabbard’s office says she accepted an invitation from organizers to join the veterans who are standing at Standing Rock.

In particular, she says, she wants to draw attention to threats to the Standing Rock Sioux tribe’s water supply, as well as the water supply of people living in communities downstream from where the pipeline would cross underneath the Missouri River.

“I’m participating in the Dakota Access Pipeline protest because of the threat this project poses to water resources in four states serving millions of people,” says the congresswoman, who has a long record of environmental activism. “Whether it’s the threat to essential water sources in this region, the lead contamination in Flint, Michigan, or the threat posed to a major Hawaii aquifer by the Red Hill fuel leak, each example underscores the vital importance of protecting our water resources.”

Earlier this year, Gabbard broke with Democratic Party leaders to support the insurgent presidential campaign of Vermont Senator Bernie Sanders, another critic of the 1,170-mile Dakota Access Pipeline. Gabbard is calling on President Obama to “do the right thing and stop this pipeline project before water resources for millions are forever ruined.” Sanders says the president should “Tell the Army Corps of Engineers that we know—we don’t need any more studies to know—that in the midst of a great crisis, a global crisis with regard to climate change, every environmental study will tell you: Do not build this pipeline. And if there are other approaches, such as declaring Standing Rock a federal monument, let’s do that.”

“For hundreds of years, the Native American people in our country, the first Americans, have been lied to, have been cheated, and their sovereign rights have been denied them,” argues the senator. “[It] is time for a new approach to the Native American people, not to run a pipeline through their land.”