The Army Corps of Engineers will grant the final approval needed to complete the controversial Dakota Access oil pipeline as soon as Wednesday, it told lawmakers Tuesday.

The news from the Army Corps, in letters to Congress and to a federal judge in Washington, D.C., came two weeks after President Trump issued a memo asking the agency to approve the pipeline as soon as possible.

The Army Corps also told the court that it will no longer complete an intensive environmental impact statement on the pipeline, an action the Obama administration decided to take in December that would have delayed the project for potentially a year or more.

The decision is a major victory for pipeline developer Energy Transfer Partners and the oil industry and a defeat for environmentalists and the Standing Rock Sioux Tribe.

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Energy Transfer told the federal judge Monday that that it could take as little as 60 days to finish the pipeline once it gets the Army Corps easement, Reuters reported.

The easement allows Energy Transfer to build the line under federally owned Lake Oahe in North Dakota. The pipeline, when complete, will run in North Dakota, South Dakota, Iowa and Illinois. Its construction is substantially complete, with the Lake Oahu portion behind the last major hurdle.

The approval had been held up for months amid objections from the Standing Rock Sioux, whose reservation abuts the lake. The tribe said the pipeline threatens its water supply.

The Standing Rock Sioux Tribe outlined its plans to fight against the pipeline in a statement on Tuesday, saying it would continue litigation against the project and urge policymakers in Washington oppose it.

“We are a sovereign nation and we will fight to protect our water and sacred places from the brazen private interests trying to push this pipeline through to benefit a few wealthy Americans with financial ties to the Trump administration,” tribal chairman David Archambault said in a statement.

Tribal lawyers have insisted Trump administration officials cannot overturn the December decision, and a lawyer for the tribe called such a decision “unlawful” during a Monday court hearing, according to Reuters.

Standing Rock’s concerns blossomed into a monthslong protest with thousands of people from around the world at the construction site urging the federal government to cancel the project.

It quickly became a flashpoint for environmentalists and indigenous-rights advocates, who accused the federal government of ignoring the Standing Rock Sioux’s objections.

But the oil industry and Republicans rallied behind Energy Transfer and said that former President Obama’s delays of the project threatened the rule of law.

Jan Hasselman, an attorney with Earthjustice who represents the Standing Rock tribe, said the Trump administration’s action is illegal and threatened court action over it.

“The Obama administration correctly found that the tribe’s treaty rights must be respected, and that the easement should not be granted without further review and consideration of alternative crossing locations. Trump’s reversal of that decision continues a historic pattern of broken promises to Indian tribes and a violation of treaty rights,” he said in a statement.

“Trump and his administration will be held accountable in court.”

Devin Henry contributed to this story.

Updated: 6:03 p.m.