Six states in the U.S. West that rely on the Colorado River to sustain cities and farms rebuked a plan to build an underground pipeline that would transport billions of gallons of water through the desert to southwest Utah.

In a joint letter Tuesday, water officials from Arizona, California, Colorado, Nevada, New Mexico and Wyoming urged the U.S. government to halt the approval process for the project, which would bring water 140 miles (225 km) from Lake Powell in northern Arizona to the growing area surrounding St. George, Utah.