Sanders said he supports building the Keystone Pipeline if President Barack Obama supports the project.
Sanders, who is running for the Democratic presidential nomination, told MSNBC on Friday that he has no objection to the pipeline, which is the subject of a presidential review by the State Department.
The Vermont senator said he does not think the pipeline will pass environmental muster and that he would support it if Obama were to sign off on the pipeline.
The pipeline would run from Canada to Texas, where it would cross the Gulf of Mexico to cross the Atlantic.
Sanders said he would oppose the project if President Donald Trump were to veto it.