Canadian Prime Minister Stephen Harper predicted Monday that the United States will approve construction of the last leg of the controversial Keystone XL pipeline from Canada.

"I am confident that in due course -- I can't put a timeline on that -- that the project will one way or another proceed," Harper told a gathering of the Vancouver Board of Trade.

US President Barack Obama is expected to decide this year whether to greenlight the 1,179-mile (1,897 km) pipeline to carry oil extracted from Alberta's oil sands south to Texas refineries.

The project was first proposed back in 2008, but after years of delays, operator TransCanada split it in two, and construction began on a southern section that did not require presidential approval.

A review on the impact of the northern section, which would cross through environmentally sensitive areas in the US state of Nebraska, is ongoing.

Opponents say extracting oil from Alberta's oil sands produces more of the carbon emissions that cause climate change as it must be steamed and separated from the sands.

Industry groups and Republican US lawmakers have promoted the project as a job creator and Canada bills itself as a safer source of energy for the United States than oil producers in the Middle East.