Agency officials took part last month in an "armed inspection" to several gold mines near the remote town of Chicken, Alaska.
Rhenium Mining News
The polemic Pebble Mine project has sparked fresh opposition after BBC World News' Monday report.
Agency quoted research conducted by anti-mining groups in its latest review of the project.
Primary and secondary resources are sufficient to allow producers and potential producers to keep pace with demand.
Arguably the richest prize in mining, the Pebble project pits a watershed where up to 40 million salmon spawn each year against copper and gold reserves worth as much as $500 billion according to a new documentary.