The White House says President Obama will veto any congressional legislation that approves the Keystone XL pipeline.
"If this bill passes this Congress, the president wouldn't sign it," White House Press Secretary Josh Earnest said.
The House, which has a Republican majority, is expected to vote on a Keystone bill this week. The GOP-dominated Senate is considering a similar measure, which has bipartisan support.
The pipeline, which would move crude from Alberta, Canada, to the Gulf of Mexico, has been at the center of a long and contentious debate involving politicians, energy companies and environmentalists, as NPR's Scott Horsley and Jeff Brady reported last November.
Supporters of the pipeline say it will create 42,000 jobs, but opponents cite environmental concerns and are skeptical about how many jobs the project can actually create — with one estimate noting that it would create just 35 permanent jobs.
A State Department environmental review of the project found Keystone wouldn't have an significant impact on greenhouse gas emissions. As to where Obama stands on the pipeline, here's more from NPR's Horsley and Brady:
"The president has unusual leverage over this pipeline. Because it crosses the U.S. border with Canada, Keystone XL requires a 'presidential permit.' Obama has guarded that power jealously. Three years ago, when Congress tried to force him to make a decision by issuing a 60-day deadline, he simply rejected the permit application.
"The political challenge for Obama is that Democrats are genuinely divided on the issue, with construction unions favoring the project and some environmental activists opposing it. No matter what he decides, some constituents will be unhappy — so the president has basically stalled."
The U.S. State Department is conducting a review of the pipeline's route, but that process has been held up because of a lawsuit in Nebraska over where the pipeline will be located.