SNC-Lavalin Group Inc. said late Thursday it has agreed to sell its AltaLink power transmission unit in Alberta for 3.2 billion Canadian dollars ($2.92 billion) to Berkshire Hathaway Energy.

The sale is part of the Montreal-based construction giant's plan to move away from its infrastructure investments to focus on its key engineering and construction operations.

SNC-Lavalin started looking at options for AltaLink, the western Canadian province of Alberta's largest regulated electricity transmission company, last September. At the time, it said it would consider a private sale, public-market alternatives or a strategic partnership.

AltaLink will operate as separate unit of Berkshire Hathaway Energy, a unit of Warren Buffett's Berkshire Hathaway Inc., and will continue to be based in Calgary, the companies said in a joint release Thursday.

"The acquisition of AltaLink represents a great long-term opportunity to invest in Alberta's critical transmission infrastructure and in Canada," said Greg Abel, chairman, president and chief executive of Berkshire Hathaway Energy.

The sale is subject to regulatory approvals, including Alberta Utilities Commission and Canadian government approvals.

As part of the deal, the companies said they have also agreed to jointly pursue transmission and distribution-development opportunities in the U.S. and Canada.

SNC unveiled plans a year ago to target growth in key engineering and construction markets, with a focus on the resources sector.

"The sale of AltaLink will help us build value for our company by providing opportunities to advance our E&C growth strategy. The use of capital will be determined based on the best long-term interests of SNC-Lavalin," said Robert Card, SNC's president and chief executive.

Write to Judy McKinnon at judy.mckinnon@wsj.com

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