The Vancouver-based company, whose attempts to mine the Alaska deposit has run into environmental opposition, said in a statement it would publish a rebuttal on its website by the end of the week. It promised to expose the "many inaccuracies and outright misstatements" in the report by New York-based Kerrisdale Capital.

Northern Dynasty's share price retraced from its lows after the company's statement. It was last down 17 percent at $2.64 on the American Stock Exchange, after earlier plunging to $1.92 on the report.

Kerrisdale said in its report that the upfront capital costs necessary to build and operate the Pebble project in Alaska are "so onerous that the mine isn't commercially viable".

"We believe Northern Dynasty is worthless," said the fund, which said it was short the company's stock.

Northern Dynasty said the report cited no technical or scientific studies and instead relied on "many unnamed persons who were purported to have been involved with the project several years ago".

Up to Monday's close, Northern Dynasty's stock had risen more than four-fold since Donald Trump's election as U.S. president in November as investors bet his administration would let an application for the stalled mine proceed.

Ronald Thiessen, Northern Dynasty's chief executive officer, told Reuters in December that he expected the U.S. Environmental Protection Agency to announce in the first quarter of 2017 that it will let the application process proceed.

The project in Alaska's Bristol Bay region holds one of the world's biggest deposits of copper and gold. But its location near a bay that supports the world's largest fishery of sockeye salmon has raised strong opposition from environmental groups, native residents and commercial and sport fishermen.

(Reporting by Nicole Mordant in Vancouver; Editing by David Gregorio)