A utility is putting a major power plant project in New Mexico on hold because Arizona regulators are considering the possibility of deregulating retail electricity sales in Arizona.

Arizona Public Service Co. said it is delaying plans to purchase Southern California Edison's shares of two units of the coal-fired Four Corners Power Plant in northwestern New Mexico and to retrofit the units for emissions compliance.

APS said the Arizona Corporation Commission's decision to accept comment on the possibility of deregulation creates uncertainty for the project, which has a total cost approaching $600 million.

The Arizona Capitol Times reported that APS disclosed its decision in a June filing with regulators.

APS and Southern California Edison share ownership of the plant with other utilities in Arizona, New Mexico and Texas.