Four hundred Arizona copper workers will be losing their jobs in the next few months. Uncertainty over a land exchange that has been stalled in Congress, is forcing the layoffs, according to the mine owners. KJZZ’s Al Macias reports.

The proposed land exchange would give the federal government more than 5,000 acres of land for conservation. In return, Resolution Copper Mining would get 2,400 acres of national forest land. Resolution Copper says the swap is critical for its expansion plans.

The exchange is opposed by some conservationists and Native American tribes.

The swap was approved by the House last year but has been stalled in the Senate. In its proposal the company said mining operation could have employed thousands of people over the next several decades.

The company says the layoffs will start by the end of December and wrap up by the end of March