WASHINGTON — President Trump greenlighted the long-delayed Keystone XL pipeline on Friday, declaring it a ‘‘great day for American jobs’’ and siding with energy advocates over environmental groups in a heated debate on climate change.

The presidential permit comes nearly a decade after Calgary-based TransCanada applied to build the $8 billion pipeline, which will snake from Canada through the United States. Trump’s State Department said the project advances US national interests, in a complete reversal of the conclusion former president Barack Obama’s administration reached less than 18 months ago.

‘‘It’s a great day for American jobs and a historic moment for North America and energy independence,’’ Trump said, standing alongside TransCanada’s CEO in the Oval Office. Keystone will reduce costs and reliance on foreign oil while creating thousands of jobs, he said, adding: ‘‘It’s going to be an incredible pipeline.’’

The decision caps the long scientific and political fight among advocacy groups over a project that became a proxy battle in the larger fight over global warming. And Friday’s decision, while long foreshadowed by Trump’s public support for Keystone, represents one of the biggest steps to date by his administration to prioritize economic development over environmental concerns.

TransCanada, Trump said, can now build Keystone ‘‘with efficiency and with speed.’’ Though it still faces other major hurdles, including disputes over the route, the president said the federal government was formulating final details ‘‘as we speak.’’

The 1,700-mile pipeline, as envisioned, would carry oil from tar sands in Alberta, Canada, to refineries along the Texas Gulf Coast, passing through Montana, South Dakota, Nebraska, Kansas, and Oklahoma. It would move roughly 800,000 barrels of oil per day, more than one-fifth of Canada’s oil, to the United States.

Environmentalists, Native American groups, and landowners who’ve opposed Keystone expressed outrage, and Greenpeace said the United States was ‘‘moving backwards’’ on climate and energy policy.

‘‘Keystone was stopped once before, and it will be stopped again,’’ vowed Annie Leonard, the group’s US director.

Associated Press