FREDONIA, Ariz. (AP) -- A popular mountain biking trail that overlooks the North Rim of the Grand Canyon is being extended.

The 18-mile Rainbow Rim trail on the Kaibab National Forest is a single-track trail that passes through ponderosa pines and drops into steep-sided canyons with aspen groves and small meadows.

Forest spokesman Patrick Lair says it's the only trail designed for mountain bikers that follows the North Rim of the Grand Canyon, although hikers and horseback riders use it as well.

Work to extend the trail by up to 8 miles to create a loop is set to begin in June, if funding is available.

The Rainbow Rim trail was constructed in the 1980s.