A U.S. appeals court has put the brakes on the transfer of federal forest land in Arizona to a company that plans to mine one of the largest copper deposits in North America.

A U.S. district judge in Arizona has opened the door for the next round of legal wrangling as environmentalists and some Native Americas seek to stop the federal government from transferring land in Arizona for a massive copper mining project.

Native American tribal members fighting plans for an enormous copper mine on land they consider sacred say they are increasingly worried U.S. officials will move forward on the project even as they await a federal appellate court ruling in the case.