It said the US Army Corps of Engineers, which issued a negative Record of Decision for the controversial project in November, had assigned a new review officer to the appeal after the previous person was promoted out of the position. 

Although Pebble was previously told the process for its appeal lodged in January would probably take longer than 90 days, it had since been informed it was now "likely to take a year or more given the complexity of the case and the scope of the administrative record which contains circa 200,000 documents".

"We have been, and continue to be, very concerned about the USACE's schedule and timeline for advancing our administrative appeal of the Pebble permitting decision, as we believe this does not accord with regulation," president and CEO Ron Thiessen said.

Meanwhile a rare 8.1 magnitude earthquake in Alaska on July 28 had resulted in "substantially less ground movement at the project site than the seismic events considered" in the assessment of the stability of Pebble's proposed tailings facility designs, the company said last week.

The project has long been opposed due to environmental and fisheries concerns and was effectively vetoed during the Obama administration.

It made progress during Trump's presidency and the company suspected political interference when the November rejection came weeks after Joe Biden's election. 

The company expects the new review officer to set a detailed timeline for the administrative appeal process, including scheduling a potential site visit and appeal conference, in the weeks ahead.

Northern Dynasty describes Pebble as "the most significant undeveloped copper and gold resource in the world" and says the initial 20 years could deliver an average annual 318 million pounds of copper, 362,000 ounces of gold, 1.8 million ounces of silver, 14Mlb of molybdenum and 12,000kg of rhenium.

Northern Dynasty shares (TSX: NDM) have fallen from about C$2 a year ago to close at 47c yesterday, capitalising it at $247.7 million (US$196 million).