March 16 (Reuters) - Rio Tinto said on Monday it has gained control of acreage in Arizona needed to build the Resolution Copper mine, a project slated to become one of the largest U.S. sources of the critical mineral but one that Native Americans have opposed for more than 20 years.

The move marks what is likely the end of a long-running and complex legal fight in which the religious rights of the San Carlos Apache people were pitted against rising demand for copper for the energy transition and Washington's efforts to wean itself off foreign supplies.

Anglo-Australian miner Rio Tinto gave the U.S. Forest Service 5,400 acres (8.4 square miles) of land in Arizona in exchange for access to 2,400 acres that contain more than 40 billion pounds (18.1 million metric tons) of copper, a crucial building block for electric vehicles, cables, and electronic devices.

The land swap came after a U.S. appeals court last week again rejected requests to block it and the U.S. Supreme Court did not take emergency measures to step in.

Rio said it would now launch a $500 million drilling campaign to explore the deposit, a necessary step before the company can forecast when copper production could begin.

Representatives for the San Carlos Apache and their attorneys were not immediately available to comment. The tribe has long said Washington had no right to the land that it swapped with Rio, going so far as to file a property lien in 2021.

"This responsible mining project fulfills President Trump's vision of American mineral independence," U.S. Agriculture Secretary Brooke Rollins said on Monday. The Agriculture Department controls the U.S. Forest Service.

COURTS REPEATEDLY REBUFFED APACHE CALLS TO BLOCK MINE

The San Carlos Apache and their allies fought for years to stop the land swap, arranged by Congress in 2014, because the mine will eventually swallow a site known as Oak Flat, or Chi'chil Biłdagoteel in the Apache language, where many worship their deities.

Multiple courts, including the Supreme Court, have repeatedly rejected their requests to block Resolution.

Trump publicly voiced support for the project last August. In a post on his Truth Social platform at the time, he said those who opposed the mine "are Anti-American, and representing other copper competitive Countries."

Rio and minority partner BHP Group ( BHP ) have spent more than $2 billion on the project without producing any copper.

"As demand for copper continues to grow, projects like Resolution can play an important role in strengthening domestic supply chains," said Katie Jackson, head of Rio's copper business.

BHP, which controls 45% of the project to Rio's 55%, said that Resolution "is positioned to be an engine for economic growth in the U.S., creating thousands of high-value, local jobs and billions in economic activity nationwide."