The Pile River flows into Alaska's Lake Iliamna. The lake and its tributaries are the headwaters of the Bristol Bay region. Photo: Luis Sinco/Los Angeles Times via Getty Images

The Trump administration will place new hurdles in front of plans to build a large gold and copper mine in a sensitive Alaskan ecosystem, and may block the project outright, according to reports Saturday.

Driving the news: The Washington Post and the Wall Street Journal report the U.S. Army Corps of Engineers will say Monday that the Pebble Mine would cause "significant degradation."

  • The agency will require major new environmental mitigation measures before the project in Alaska's Bristol Bay watershed can receive needed approvals.
  • Politico reports that the Trump administration plans to outright block the project, marking a "surprise reversal" of earlier support.

The intrigue: The reportedly imminent steps follow opposition to the project from key supporters of President Trump, including his son Donald Trump, Jr.

  • Other opponents include Fox News' Tucker Carlson and Nick Ayers, who is former chief of staff to Vice President Mike Pence.

Why it matters: The project, which the Obama administration did not allow to proceed, is proposed in a region that's home to the world's largest sockeye salmon fishery. Environmentalists, outdoor enthusiasts and fishing industry groups oppose the mine.

  • Even imposing new requirements could further endanger the project, because Democratic White House nominee Joe Biden opposes the Pebble Mine too.

Yes, but: Pebble Limited Partnership CEO Tom Collier is expressing confidence that the project can advance with new environmental protection steps.

  • "They’re going to expect a substantial amount of mitigation. But we’ve known that for a months. … That’s something we expect can be dealt with in due course," he told the Post.
  • And per the WSJ: "Mr. Collier said his team is working on a new mitigation proposal he expects to be finished within a few weeks and lead to a resolution with the Corps before Election Day."

Of note: "The White House is not in a position to comment on this at this time," spokesman Judd Deere told Axios. The Army Corps did not provide immediate comment.

Go deeper: Army Corps rules Alaskan mine will not harm salmon fishery

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