WASHINGTON (AFP) - True to his pledge, President Donald Trump gave final approval on Friday (March 24) for TransCanada to build the controversial Keystone XL oil pipeline, overriding environmental concerns in favor of boosting jobs and energy supply.

"It's a great day for American jobs and a historic moment for North America and energy independence," Trump said at the White House.

He also promised to call the governor of Nebraska to help the company secure the necessary construction permits.

Barack Obama blocked the project, first proposed in 2008, over environmental concerns, but Trump says the pipeline will create thousands of jobs and provide affordable energy.

During the US presidential campaign, Trump repeatedly promised to approve the pipeline, and one of his first acts after taking office in January was to give a conditional go-ahead for the cross-border project.

It is all part of his plan to boost the economy, improve infrastructure, slash regulations and reduce government interference he says is hindering business.

But the jobs promise is subject to dispute. The State Department estimated the US-portion of the pipeline would create 42,000 temporary jobs over a two-year construction period, but opponents note that less than 50 permanent jobs would be created for pipeline maintenance.

HEAVY CRUDE TO THE GULF

Keystone XL is an expansion of TransCanada's existing system to funnel bitumen from Alberta's oil sands to refineries on the US Gulf Coast.

The portion blocked by the Obama administration was a US$5.3 billion (S$7.4 billion) proposal to build a 1,900km pipeline to Nebraska, with some 1,400km winding through the United States, which would carry 830,000 barrels of oil per day.

After a new US review of the project, Under Secretary of State Thomas Shannon issued the presidential permit, concluding that it would "serve the national interest," the State Department said Friday.

TransCanada thanked the US administration for reviewing and approving the delayed project.

"This is a significant milestone for the Keystone XL project," said TransCanada president and chief executive officer Russ Girling, who was with Trump at the White House.

The company looks forward to working with the White House "as we continue to invest in and strengthen North America's energy infrastructure," he said in a statement.

The company has a total of US$15 billion in investment in oil and natural gas "that will create thousands of well-paying jobs and generate substantial economic benefits across the US." But TransCanada still will need to work with authorities and residents to obtain the necessary permits and approvals for construction in Nebraska, Montana and South Dakota, the company said.

Protestors supporting the Standing Rock Sioux Native American tribe for many months blocked completion of a section of the Dakota Access pipeline in North Dakota, until the Trump administration overrode their environmental concerns and approved the construction.

ENVIRONMENTAL PROTESTS CONTINUE

Environmental groups immediately expressed outrage at the Keystone XL approval and vowed to continue to fight the project, so the company could face obstacles at the state and local level. One protest is set for Friday evening at the White House.

Michael Brune, head of the Sierra Club, the largest US environmental organisation, called the pipeline approval "yet another decision made by Trump that would be disastrous for our climate, our communities, and our health."

"The dirty and dangerous Keystone XL pipeline is one of the worst deals imaginable for the American people, so of course Donald Trump supports it," he said in a statement.

He warned that the project "faces a long fight ahead in the states."

Opponents object to the pipeline because it further promotes the use of fossil fuels - although there already are hundreds of oil and gas pipelines crisscrossing the United States - but say Canada's oil sands are particularly harmful.

Canada is the world's sixth-largest oil producer thanks to the Alberta oil sands.

Unlike traditional crude which gushes from a well, bitumen from the oil sands must be dug up or extracted by underground heating, essentially using steaming hot water to separate it from the sandstone before it can be refined.

This takes vast amounts of water resources and results in huge ponds of polluted water and the strip-mining of once-pristine boreal forests.

Environmentalists also say the bitumen in oil sands is harmful and corrosive, which makes pipeline ruptures or leaks more likely and carries greater health and safety risks.

However, TransCanada defends its safety record and says buried pipelines are far safer for transporting oil than ships or trains.

Trump concurred, saying, "I think it's a lot safer to have pipelines than to use other forms of transportation for your product."