A Trans Mountain official said last week that start-up was expected in early April, with volumes ramping up to full capacity by the end of the year.

The C$30.9-billion ($23.04 billion) expansion project will nearly triple the flow of crude from Alberta to Canada's Pacific Coast to 890,000 barrels per day, but has been plagued by years of delays and cost overruns.

The main challenge remaining for the expansion project is the installation of a section of pipeline through a mountain in British Columbia, which the company had said it expected to complete early this week.

Trans Mountain's delays in the past two months have lowered Canadian heavy oil prices, but the company thought such problems were behind it after a regulator approved its construction change.

The discount on Western Canadian Select for April delivery against the North American benchmark grew to $16.35 per barrel, compared with $14.80 before Trans Mountain announced the latest delay, a market participant said. The bigger discount reflected concerns about constrained pipelines due to Trans Mountain's latest delay.

($1 = 1.3414 Canadian dollars)

(Reporting by Rod Nickel in Winnipeg and Rahul Paswan in Bangalore; editing by Jonathan Oatis; Editing by Marguerita Choy)