“I think it is imperative that we look at the Keystone pipeline as what I think it is, as a distraction to the important work we have to do on climate change,” she said. "And unfortunately, from my perspective, one that interferes with our ability to move forward with all the other issues."
“Therefore I oppose it,” she said. “I don’t think it's in the best interest to combat climate change.”
As President Obama’s secretary of State from 2009 to 2013, Clinton oversaw the Obama administration’s consideration of TransCanada Corp.’s application to build the pipeline from Alberta, Canada’s oil sands to Texas’s Gulf Coast.
Saturday marked seven years since the firm first submitted its application to build Keystone, and Obama has refused to decide on the permit, even when Congress gave him a deadline.
Since declaring her candidacy for president earlier this year, Clinton had refused to state a position on the project, saying that her previous involvement with the issue while at Foggy Bottom means she should not wade into it.
She also noted that she had told the White House just weeks ago that she could not remain silent much longer.
So when she was asked about Keystone on Tuesday, Clinton said "I had put people on adequate notice that I would respond when asked, and I said that I did oppose it."
Clinton's announcement could help her on the left with environmental groups, and some immediately cheered her announcement.
“We are thrilled that Secretary Clinton has continued to build on her longtime environmental leadership by publicly opposing the dirty and dangerous Keystone XL tar sands pipeline,” said Tiernan Sittenfeld, senior vice president of government affairs a the League of Conservation Voters Action Fund.
“This is exactly the kind of leadership we need in order to leave a healthy planet for our children and grandchildren.”
Oil interests, Republicans and even some Democrats see the pipeline as an essential step toward increasing the share of energy that the United States gets from friendly allies, while creating thousands of construction jobs.
But environmentalists say it would spur more development of Canada’s oil sands, which are far more polluting than traditional varieties of crude oil.
After extensive analysis, the State Department said last year that Keystone would not significantly impact the environment or climate. Environmentalists have balked at that conclusion and said that the low oil prices of the last year mean the pipeline will make oil sands development easier.
Congress earlier this year approved legislation to build the pipeline, but it was vetoed by Obama.
“As someone who says he is committed to action on climate, it is long past time for President Obama to reject Keystone XL," Zarlin added.
The White House had no immediate comment on the announcement.
Sanders lauded Clinton's announcement, though he noted the time it took her to reach the decision.
“As a senator who has vigorously opposed the Keystone pipeline from the beginning, I am glad that Secretary Clinton finally has made a decision and I welcome her opposition to the pipeline," he said. "Clearly it would be absurd to encourage the extraction and transportation of some of the dirtiest fossil fuel on the planet.”
Former Maryland Gov. Martin O'Malley, who remains far behind both Clinton and Sanders in the polls, was more critical, and suggested Clinton was failing to lead on the issue.
"On issue after issue — marriage equality, drivers licenses for undocumented immigrants, children fleeing violence in Central America, the Syrian refugee crisis, and now the Keystone Pipeline, Secretary Clinton has followed — not forged — public opinion. Leadership is about stating where you stand on critical issues, regardless of how they poll or focus group," he said.
GOP presidential hopeful Jeb Bush blasted the announcement, suggesting that killing the pipeline would hurt the economy.
"@HillaryClinton finally says what we already knew," the former Florida governor tweeted. "She favors environmental extremists over U.S. jobs."
The oil and gas industry, a strong backer of Keystone XL, also criticized Clinton.
The American Petroleum Institute (API) said Clinton’s position is “wrong” and in opposition to American voters, 68 percent of whom support the project, according to a poll the group commissioned.
“Hillary Clinton’s decision to oppose Keystone is a missed opportunity to seize the true potential of our energy renaissance,” API President Jack Gerard said in a statement.
“It is most unfortunate for American workers and consumers that she has joined the forces of delay and denial.”
Green group 350 Action credited the actions of its activists and others for pressuring Clinton to come out in opposition. Volunteers associated with the group have repeatedly asked Clinton at public events about Keystone, and one took a photo with her last week with a sign that said “I’m ready for Hillary to say no KXL.”
“Thanks to thousands of dedicated activists around the country who spent years putting their bodies on the line to protect our climate, we’ve taken a top-tier presidential candidate’s ‘inclination to approve’ Keystone XL, and turned it into yet another call for rejection,” May Boeve, the group’s executive director, said in a statement.
“Her position on Keystone should set an important precedent for her policies going forward: we cannot afford to approve projects that make climate change worse.”