The Trump administration is reportedly planning to block the proposed controversial Pebble Mine project in Alaska this week, according to Politico, marking a surprise reversal that could be the death knell for the massive copper and gold project.

Environmentalists and conservation groups have warned that the project would threaten world’s largest sockeye salmon fishery, and the move to block it comes after President Trump faced pressure from numerous forces, including his son, to nix it.

The Army Corps of Engineers office in Alaska is planning to hold a conference call on Monday with groups connected to the proposed mine discuss the decision, said Politico.

Sources told the media outlet Corps officials will say outstanding technical issues with a key permit remain, adding they anticipate Trump will then follow with a public statement opposing the project.

“The White House is not in a position to comment at this time," White House spokesman Judd Deere told Politico. Neither the Army Corps nor EPA immediately responded to requests for comment.

The about-face by the administration likely signals more about issues with this specific mine than a sea change in Trump’s overall support for big development projects.

But with Trump expected to let it die and his White House challenger Democrat Joe Biden opposed to the project, Pebble Mine appears to have few options to advance it despite more than a decade of planning, ownership changes and political fights.

At the end of July, Trump’s administration appeared to be on track to approve the project as early as this month over the protests of environmentalists and Alaskan Native groups opposed to the 8,400-acre open pit mine.

Trump's son Donald Jr. also publicly raised the issue of the controversial mine project, tweeting along with Nick Ayers, former chief of staff to Vice President Mike Pence, to urge Trump to reject Pebble.

The duo cited outdoors recreation groups' concerns that it threatens the Bristol Bay salmon fishery, which is commercially important and an increasingly popular destination for anglers.