The Obama administration said this week it is continuing a review of the proposed Keystone XL oil pipeline, despite a request by the project's developer to suspend the review.
If granted, a delay could have put off a decision on the high-profile project until the next U.S. president takes office in 2017. President Barack Obama has yet to say whether he would approve or reject the pipeline, but the Democrats running for president have all said they oppose it while Republican candidates support it.
State Department spokesman John Kirby said the department advised TransCanada on Wednesday of its decision to continue the review. The State Department has jurisdiction over the pipeline because it crosses a U.S. border.
Kirby said there was no legal requirement for officials to suspend the review, adding that "a lot of interagency work" has gone into the evaluation so far. Secretary of State John Kerry "believes that it's most appropriate to keep the process in place," Kirby said.
Calgary-based TransCanada asked the U.S. on Monday to delay consideration of the Alberta-to-Texas pipeline, the latest wrinkle in a seven-year quest for the project.
TransCanada said it respects the U.S. decision and will continue its efforts to demonstrate that the long-delayed pipeline - a flashpoint in the global debate over climate change - is in the U.S. national interest.
Five reports and 17,000 pages of State Department review have shown the project's benefits over the past seven-plus years, said TransCanada spokesman Mark Cooper.
"The fundamental question remains: Do Americans want to continue to import millions of barrels of oil every day from the Middle East and Venezuela or do they want to get their oil from North Dakota and Canada through Keystone XL?" Cooper said. "We believe the answer is clear and the choice is Keystone XL."
The 1,179-mile pipeline would run from Canada through Montana, South Dakota and Nebraska, where it would connect with existing pipelines to carry more than 800,000 barrels of crude oil a day from tar sands in western Canada to refineries along the U.S. Gulf Coast.
Opponents say the project requires huge amounts of energy and water and increases greenhouse gas emissions blamed for global warming. They also warn that pipeline leaks could potentially pollute underground aquifers that are a critical source of water for farmers in the Great Plains.
Supporters say the project will create jobs and reduce U.S. reliance on Middle Eastern oil. They argue that pipelines are a safer method of transporting oil than trains, pointing to recent derailments on both sides of the border, including a 2013 disaster in Canada that killed 47 people.
Democratic presidential candidate Bernie Sanders said Wednesday that Obama should reject the Keystone project before heading to Paris next month to finalize a global climate agreement,
The Vermont independent senator said rejecting the pipeline now would show "bold leadership" and signal to the world that the United States was serious about addressing climate change, which Sanders called "a major, major, major planetary crisis."
Sanders said he had "zero doubt" that if a Republican wins the presidential election, "on Day One the Keystone people will be back pushing for that pipeline. I think their hope is that Republicans win, and when they do the path will be open for that pipeline and other disastrous environmental legislation."
Environmental groups hailed the decision to continue the review and urged Obama to act swiftly to reject the pipeline.
The American Petroleum Institute, the oil and gas industry's top lobbying group, said polls consistently show a strong majority of Americans support the project.
Thousands of jobs and billions of dollars in wages and investment "that could be made building Keystone remain out of reach because this president refuses to make the right decision," said Louis Finkel, the group's executive vice president.