State department faces Keystone XL review
The US state department's handling of a request to build Keystone XL, a 1,600-mile (2,700km) oil pipeline, will be reviewed for wrongdoing.
Reports have surfaced that a company involved in the environmental review had listed developer TransCanada as a "major client".
The review decision comes a day after demonstrators protested against the pipeline plans outside the White House.
A review could potentially delay a final decision on the pipeline.
The state department is handling public consultations on the project as the pipeline would cross the US border with Canada, but the White House has made it clear that President Barack Obama will influence the final outcome.
The review request was led by Senator Bernie Sanders of Vermont, an independent, and Representative Steve Cohen of Tennessee, a Democrat.
"At a time when all credible scientific evidence and opinion indicate that we are losing the battle against global warming it is imperative that we have objective environmental assessments of major carbon-dependent energy projects," Mr Sanders said.
In an October letter, Mr Sanders and Mr Cohen specifically asked the state department's inspector general to look at all contractual or financial ties between the consultant, Houston-based Cardno Entrix and TransCanada.
They also asked for a review of state department emails related to a TransCanada lobbyist who had worked in Secretary of State Hillary Clinton's 2008 presidential campaign.
TransCanada, which is seeking permission to build the pipeline from Alberta to the Gulf coast in Texas, said it welcomed the review.
"We conduct ourselves with integrity and in an open and transparent manner. We are certain that the conclusion of this review will reflect that," spokesman James Millar told the Associated Press news agency.
Pollution and political risks
Environmentalists are opposed to the Keystone XL project because of the method used for extracting petroleum from Alberta's oil sands.
They are also concerned by the risk of pollution on the pipeline route.
The proposed pipeline would pass south from Alberta through the US states of Montana, South Dakota, Nebraska, Kansas and Oklahoma before ending up at refineries in Texas.
Correspondents say the decision to allow the project or not is fraught with political risk for Mr Obama.
If he rejects it, he could be accused of destroying jobs. But allowing it to go ahead could lose him the support of activists who helped propel him to the White House, they note.
On Sunday, protesters formed a human chain around the White House, with some carrying an inflatable replica of a pipeline on their shoulders.
"We have to leave the tar sands oil in the ground. That's the only solution if we are going to save the planet," protester Martin Springhetti told AP.