WASHINGTON — President Trump moved assertively on Tuesday to resurrect a pipeline in the Dakotas that had become a major flashpoint for Native Americans, while reviving the Keystone XL pipeline, which had stirred years of debate over the balance between energy needs and environmental concerns.
The actions were the latest to dismantle Obama era policies. The former president rejected the proposed 1,179-mile Keystone pipeline in 2015, arguing that it would undercut American leadership in curbing reliance on carbon energy to address a warming climate.
Mr. Trump signed a document clearing the way for the government to reconsider the pipeline as well as another expediting the Dakota Access pipeline from North and South Dakota to Illinois.
The decisions came a day after Mr. Trump formally abandoned the Trans-Pacific Partnership, an ambitious, 12-nation trade pact negotiated by Mr. Obama. In his opening days in office, Mr. Trump has also signed an order that begins to unravel Mr. Obama’s health care program, reversed the former president’s policies on abortion and housing, and ordered a freeze of any pending regulations left behind by the departing administration.
As proposed by TransCanada, a Canadian firm, the Keystone pipeline would carry 800,000 barrels a day from the Canadian oil sands to the Gulf Coast. Republicans and some Democrats argued that the project would create jobs and expand energy resources, while environmentalists said it would encourage a form of oil extraction that produces more gases that warm the planet than normal petroleum.
Studies showed that the pipeline would not have a momentous impact on jobs or the environment, but both sides made it into a symbolic test case of American willingness to promote energy production or curb its appetites to heal the planet. Torn by competing policy imperatives and conflicting politics, Mr. Obama delayed a decision for years before finally rejecting the pipeline shortly before an international conference in Paris to forge a global climate change agreement.
“Keystone has never been a significant issue from an environmental point of view in substance, only in symbol,” said David Goldwyn, an energy market analyst and a former head of the State Department’s energy bureau in the Obama administration. Regarding the pipeline’s effect on the nation’s broader energy market, Mr. Goldwyn said: “One additional pipeline? It’s useful. It’s not indispensable.”
But it was a symbol Mr. Trump found important enough to seize on early in his presidency. He signed an executive memorandum inviting TransCanada “to promptly resubmit its application to the Department of State for a presidential permit” for the pipeline, although the document did not guarantee approval.
Speaking with reporters, the president said he would “renegotiate some of the terms” — including possibly an insistence that the pipeline be built with American steel — but left little doubt that he wanted it approved. “We’ll see if we can get that pipeline built,” he said. “A lot of jobs.”
Terry Cunha, a spokeswoman from TransCanada, said in an email on Monday that the company remained “fully committed” to building the project, although she declined to discuss the project’s next steps.
The Dakota Access pipeline in North Dakota became the focus of protests when the Standing Rock Sioux Tribe objected to its construction less than a mile from its reservation. The tribe and its allies won victory last month when the Army Corps of Engineers announced that it would look for alternative routes for the $3.7 billion pipeline instead of allowing it to be drilled under a dammed section of the Missouri River.
Mr. Trump signed an executive memorandum directing the Army “to review and approve in an expedited manner” the pipeline, “to the extent permitted by law and as warranted.” In his session with reporters, he added, “Again, subject to terms and conditions to be negotiated by us.”
Mr. Trump owned stock in Energy Transfer Partners, the company that is building the Dakota Access pipeline, according to his most recent filing with the Federal Election Commission. Last month, a spokesman for Mr. Trump said he sold all of his stock in June, but there is no way of verifying that sale, and Mr. Trump has not provided documentation of it.
Critics denounced Mr. Trump’s decisions. “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,” said Michael Brune, executive director of the Sierra Club.
Environmental activists vowed to keep fighting the projects. “This is not a done deal,” Bill McKibben, founder of 350.org, the group that led the protests against the Keystone pipeline, said in a statement. “The last time around, TransCanada was so confident they literally mowed the strip where they planned to build the pipeline, before people power stopped them. People will mobilize again.”
In Canada, the government of Prime Minister Justin Trudeau welcomed Mr. Trump’s decision. “We have been supportive of this since the day we were sworn into government,” Jim Carr, the natural resources minister, told reporters in Calgary, Alberta, the center of nation’s oil industry, where the cabinet was meeting. Mr. Carr said the American reversal will lead “to a deepening of the relationship across the border.”
The green light for Keystone came after Mr. Trudeau’s approval of two pipeline projects linked to Alberta’s oil sands in late November. Expanded pipeline capacity and its potential to expand the market for the oil sands, which overwhelmingly export to the United States, are welcome developments in Alberta and neighboring Saskatchewan, both oil-producing provinces. But there is considerable opposition to Keystone and oil sands pipelines in general in other parts of Canada and within many indigenous communities.
In addition to the Keystone and Dakota directives, Mr. Trump signed three others intended to ease the way for businesses and promote American manufacturing. One instructed the Commerce Department to develop a plan to ensure that all future pipelines built in the United States be constructed out of American-made materials.
Another was aimed at streamlining what he called “the incredibly cumbersome, long, horrible permitting process and reducing regulatory burdens for domestic manufacturing.” The last directive was intended to expedite environmental reviews for “high-priority infrastructure projects” like highways and bridges.
Mr. Trump’s actions came on a day when he met with the leaders of the country’s largest automakers, whom he has been pushing to produce more of their products in the United States. He singled out General Motors in a Twitter post this month for building the Chevy Cruze hatchback in Mexico. “Make in U.S.A. or pay big border tax!” he wrote.
Hosting the automakers on Tuesday, he made a point of holding out a chair for Mary T. Barra, G.M.’s chief executive. “You’re not being singled out, believe me, Mary, I promise,” he told her as journalists recorded the moment. “But you have a lot of plants from a lot of different items built in the United States. And it’s happening, it’s happening big league.”
Mr. Trump said he understood that manufacturers faced regulatory burdens in the United States and he would make it easier for them to make their products in the country. “We’re going to make the process much more simple for the auto companies and for everybody else who wants to do business in the United States,” he said. “You’re going to find this to be from being very inhospitable to extremely hospitable.”
Anticipating criticism from advocates of tackling climate change, he added: “I am, to a large extent, an environmentalist, I believe in it. But it’s out of control and we’re going to make it a very short process. And we’re going to either give you your permits or we’re not going to give you your permits. But you’re going to know very quickly. And generally speaking we’re going to be giving you your permits.”
The auto executives offered praise for Mr. Trump after the session. “We’re very encouraged by the president and the economic policies that he’s forwarding,” Mark Fields, the chief executive of the Ford Motor Company, told reporters outside the White House as they left.
He cited the withdrawal from the Trans-Pacific Partnership. “We appreciate the president’s courage to walk away from a bad trade deal,” he said.