However, excluding the Keystone XL writedown, the company reported a higher-than-expected profit and raised its dividend at a time when most energy companies are scaling back shareholder payouts.

Calgary-based TransCanada said long-term contracts helped underpin its business during a "very challenging year", in which global crude oil prices tumbled on concerns about oversupply.

The company endured a difficult end to 2015 after U.S. President Barack Obama blocked the cross-border Keystone XL pipeline in a victory for environmentalists who campaigned against the project for more than seven years.

Last month, TransCanada filed legal action against the United States for the rejection and has vowed to press ahead with the project.

The company's proposed Energy East pipeline from Alberta to Canada's Atlantic coast has also run into environmental opposition, and new interim rules on energy project reviews imposed in January could lead to further delays. [L2N15B1QM]

"We are still assessing the impact of the NEB (National Energy Board) changes...we are still targeting 2020 but I think it's fair to assume with a extension of the regulatory process that may translate into a delay in bringing it into service," said Paul Miller, president of liquids pipelines, said on an earnings call.

Excluding the after-tax impairment charge related to Keystone XL, TransCanada's profit was 64 Canadian cents per share in the fourth quarter, higher than the average analyst estimate of 61 Canadian cents.

Net loss attributable to shareholders was C$2.46 billion, or C$3.47 per share, in the three months ended Dec. 31, compared with a profit of C$458 million, or 65 Canadian cents per share, a year earlier.

TransCanada shares closed almost flat on the Toronto Stock Exchange at C$48.24.

(Additional reporting by Tanvi Mehta in Bengaluru; Editing by Don Sebastian, Sriraj Kalluvila and Marguerita Choy)

By Nia Williams