US President Donald Trump has infuriated environmentalists by signing executive orders that support two controversial oil pipelines.
The new Republican president backed the Keystone XL and Dakota Access projects, provided American steel is used.
The Obama administration in late 2015 halted Keystone, which would carry crude from Canada to Texas.
The Army decided last year to explore other routes for the Dakota pipeline amid huge protests by Native Americans.
In the White House on Tuesday, Mr Trump said both projects would be subject to renegotiated terms and conditions.
As he signed the Keystone XL measure the president said it would create a "lot of jobs, 28,000 jobs, great construction jobs".
Campaigners have said the project will leave only a handful of long-term positions after the pipeline is built.
Signing another order calling for US steel to be used in construction of oil pipelines, Mr Trump said: "From now on we're going to start making pipelines in the United States... like we used to do in the old days."
Environmental groups reacted with outrage.
Greenpeace director Annie Leonard said that "instead of pushing bogus claims about the potential of pipelines to create jobs, Mr Trump should focus his efforts on the clean energy sector where America's future lives".
Sierra Club Executive Director Michael Brune said: "Donald Trump has been in office for four days and he's already proving to be the dangerous threat to our climate we feared he would be."
The Standing Rock Sioux Tribe, whose land abuts the proposed route of the Dakota Access pipeline, called Mr Trump's decision a violation of "law and tribal treaties", and vowed to take legal action.
"Americans know this pipeline was unfairly re-routed towards our nation and without our consent," Tribal Chairman Dave Archambault II said in a statement.
Mr Trump, who took office on Friday, promised during his White House campaign to support Keystone XL and fossil fuels, including the flagging US coal industry.
But during a Tuesday morning meeting with automobile executives at the White House, Mr Trump described himself as an environmentalist.
On Monday, he made similar comments to other business leaders, saying: "I'm a very big person when it comes to the environment. I have received awards on the environment."
Canada lobbied hard for years for the approval of the Keystone XL pipeline under former-Prime Minister Stephen Harper, who once said that authorising the new oil sands pipeline was a "complete no-brainer".
His successor, Prime Minister Justin Trudeau, also supports the project and has said he intends to work with President Trump to approve the pipeline, proposed by Calgary-based energy infrastructure giant TransCanada.
On Tuesday, Canada's natural resources minister praised Mr Trump's step.
During his campaign, Mr Trump called upon TransCanada to resubmit their proposal for a construction permit.
Keystone XL would carry Canadian oil sands crude 1897km from Alberta to US Gulf coast refineries.
The planned Dakota Access pipeline would run 1770km from North Dakota to Illinois.
Pipeline advocates argue that it is a safer means of transporting oil across the country, compared to road or rail.