DENVER (AP) — Utilities serving customers in Colorado, Wyoming and portions of adjoining states are moving to join a larger transmission system in a move they say could reduce costs.

The Mountain States Transmission Group said Friday it's moving to join the Southwest Power Pool.

The larger group has nearly 100 member companies and an electricity transmission system serving 14 states.

The Mountain West group is an informal alliance of utilities formed in 2013 serving more than 6 million customers. It includes Xcel Energy, Black Hills Energy, Basin Electric Power and others.

Supporters say the deal could bring customer benefits, but regulators warned it could leave the region more vulnerable to outages if not done right.

The deal could be finalized by late 2019.