For years, Canada’s booming oil fields have had few choices but to funnel the country’s thick, tar-like crude oil through pipelines snaking through the Midwest to the Gulf Coast. That has pushed down prices paid by many U.S. refiners and, in turn, gas stations and airports from Minneapolis to Chicago to Detroit.

 Canadian oil companies will soon have the option to ship crude through a long-delayed, 715-mile pipeline expansion to the Pacific Ocean. That will allow traders to sell more oil to the U.S. West Coast and to fast-growing Asian economies.

The Trans Mountain expansion, which will nearly triple the capacity of an existing pipeline to 890,000 barrels a day, promises to give Canadian companies more pricing power and boost the country’s position as a global energy powerhouse.

Americans guzzled Canadian oil even as U.S. crude output ballooned in recent years, turning Canada into an export juggernaut. Imports from north of the border surpassed 4 million barrels a day some months last year, U.S. officials say, nearly two-thirds of total shipments.

Those supplies have come at a bargain, as the price of Canadian oil accounts for transport costs, differences in crude quality and a limited pool of buyers. Benchmark Canadian crude cost about $18 a barrel less than its U.S. counterpart Tuesday. That differential reached $47 in 2018, forcing the government of Alberta to curtail production to support prices.

The project cleared its last major regulatory hurdle in mid-January, and workers are laying the final stretch of pipe that will carry Canadian crude from Alberta’s oil sands to the Pacific. Traders are now trying to time the startup of the project, which faces last-minute construction challenges before it can shake up the North American market.

Canadian companies have ramped up production in anticipation that more supplies may soon reach an export terminal and pipeline hookups to Washington state. November output in the prolific oil-producing province of Alberta rose to a record 4.16 million barrels a day, according to government figures.

Prime Minister Justin Trudeau vowed to finish the expansion, calling it “vital” to Canada’s strategic interests. The pipeline in January appeared to have cleared its last obstacle when the Canada Energy Regulator approved a change in the pipeline’s thickness during the final stretch of drilling.

Construction snarls, regulatory hurdles and court cases have run up government spending on the project to about $25 billion, according to the latest estimates.

The project is meant to boost a Canadian industry whose growth over the past 15 years in many ways reflects that of its hulking counterpart down south. While America’s hottest oil field in West Texas and New Mexico pumps out light, sweet crude, Alberta’s oil sands dish out heavier supplies that are generally costlier to refine.

U.S. refining officials have played down the impact on American consumers and the domestic fuel-making industry, saying the sector can tweak plant-by-plant operations based on what crude is available. But some have warned that it could siphon off supplies from the arcane business of sending tankers-full of Canadian crude to countries such as China.