CALGARY -- TransCanada Corp. (TRP.TO) has signed a deal to sell its Coolidge Generating Station in Arizona to a subsidiary of Southwest Generation Operating Co. LLC for $623 million.

TransCanada chief executive Russ Girling says the sale, worth US$465 million, is part of a plan to help fund the company's capital spending program.

The 575-megawatt natural gas-fired power in Coolidge, Ariz., is underpinned by a long-term power purchase agreement.

Under the terms of the PPA, Salt River Project Agricultural Improvement and Power District has a right of first refusal on a sale to a third party.

TransCanada owns and operates pipelines across North America as well as power generation assets including a stake in the Bruce Power nuclear power plant in Ontario.