US President Barack Obama has rejected the proposed Keystone XL oil pipeline from Canada, saying he could not vouch for its safety by a deadline, despite intense election-year pressure.
The rival Republican Party had forced Obama to make a decision on whether to approve the 2,700 km route through the Great Plains to Texas, forcing him to choose between environmentalists and industry.
The Obama administration said on Wednesday that the company TransCanada could resubmit the Keystone XL project, but that officials were not able to assess its plan by a February 21 deadline put into law by Republicans in Congress.
TransCanada has said that it would re-apply.
"This announcement is not a judgment on the merits of the pipeline, but the arbitrary nature of a deadline that prevented the State Department from gathering the information necessary to approve the project and protect the American people," Obama said in a statement.
"I'm disappointed that Republicans in Congress forced this decision, but it does not change my administration's commitment to American-made energy that creates jobs and reduces our dependence on oil," said Obama, who initially hoped to make a decision after the November election.
The pipeline has turned into a major issue in US politics, with environmentalists waging months of street protests against it and the oil industry funding an advertising blitz, saying the project would immediately create shovel-ready jobs amid a weak economy.
Canadian Prime Minister Stephen Harper expressed "profound disappointment" to Obama over the rejection, telling him in a telephone call that he had hoped this project "would continue given the significant contribution it would make to jobs and economic growth" in both countries.
Mitt Romney, the frontrunner for the Republican nomination to challenge Obama in November, meanwhile called the Democratic president's decision "as shocking as it is revealing."
"The president demonstrates a lack of seriousness about bringing down unemployment, restoring economic growth, and achieving energy independence," Romney said in a statement as he campaigned in South Carolina.
House Speaker John Boehner vowed that Republicans would keep looking for ways to force through approval of the oil pipeline.
"The president won't stand up to his political base, even in the interest of creating jobs," Boehner told reporters.
'An iconic victory'
Environmentalists had raised fears of an accident along the 2,700km proposed route, which would go through the uniquely sensitive terrain of Sand Hills in Nebraska where there is wide opposition.
Anti-Keystone protest leader Bill McKibben, founder of the activist group 350.org, hailed Obama for standing up to the "fossil fuel lobby," which he said was in control of Congress.
"Assuming that what we're hearing is true, this isn't just the right call, it's the brave call," he said in a statement.
"The knock on Barack Obama from many quarters has been that he's too conciliatory. But here, in the face of a naked political threat from Big Oil to exact 'huge political consequences,' he's stood up strong," McKibben said.
Damon Moglen, climate and energy director at Friends of the Earth, called the decision "an iconic victory" in the fight against climate change.
"The Keystone XL fight was David versus Goliath -- no one thought we could win," Moglen said.