Obama will decide on Keystone pipeline during his term
The White House has said it intends to rule on the fate of the Keystone XL oil pipeline before the end of President Barack Obama's term.
The company behind the pipeline, TransCanada, had wanted to delay the approval process until after his term.
The White House said on Tuesday "there might be politics at play" in the decision by TransCanada.
Some analysts think the company is waiting in hopes that the next president would welcome the project.
The company had complained for years about delays from the Obama administration and had aggressively urged that the project be approved as quickly as possible.
The Keystone XL would send more than 800,000 barrels a day of mostly Canadian oil to Nebraska. From there, the oil would travel to refineries and ports along the US Gulf Coast.
The project has pitted Republicans and other supporters - who say it will create much needed jobs - against many Democrats and environmentalists, who warn the pipeline will add to carbon emissions and contribute to global warming.
President Obama vetoed a Republican bill approving the pipeline in February.
All the Democratic candidates for president - including front-runner Hillary Clinton - oppose the project. The Republican field supports the pipeline.
Outgoing Canadian Prime Minister Stephen Harper was a strong proponent of the pipeline, but his successor Justin Trudeau - while supportive - is less bullish on the scheme.
The Keystone XL pipeline project was first proposed more than six years ago, but has languished, awaiting a permit required by the federal government because it would cross an international boundary.