Two of the world’s largest coal producers have announced they will combine mining operations in Colorado and Wyoming in an attempt to improve their competitiveness against natural gas and renewable energy sources.

Arch Coal and Peabody Energy are based in St. Louis and announced the joint venture on Wednesday.

It will be 66.5% owned by Peabody and 33.5% owned by Arch.

The companies say the deal, requiring approval from regulators, could save about $120 million annually in mostly operational costs over 10 years.

The plan involves the North Antelope Rochelle, Black Thunder, Caballo, Rawhide and Coal Creek mines in Wyoming and the West Elk and Twentymile mines in Colorado.

The mines employed about 3,300 workers in 2018.

The companies gave no guidance on future employment levels.