It's the second letter sent to Obama within a month calling for immediate approval of the project.
"I can’t see how it will be otherwise," Prime Minister Stephen Harper said of the pipeline.
Rejecting the Keystone XL pipeline would be "political" and would “definitely strain” U.S.-Canadian relations, Canada's ambassador to Washington warned.
The Texas senator is shifting his focus to U.S. energy policy.
Highways will be a focus of lawmakers this week as the Senate holds hearings on the funding for future road construction and the costs of not be prepared for weather emergencies.
The Senate Environment and Public Works Committee will hold a hearing on the necessity of a reauthorization of the 2012 Moving Ahead for Progress in the 21st Century (MAP-21) bill.
Officials with the panel said the hearing would focus on “the economic importance of maintaining federal investments in our transportation infrastructure.”
The budget office forecasts the bill would require new revenues to maintain spending levels.
The Hill takes a deep dive into transportation funding issues in Thursday's print edition, featuring opinion pieces from House Transportation Committe Chairman Rep Bill Shuster (R-Pa.), Sen. Mark Warner (D-Va.) and former Transportation Secretary Ray LaHood.
Salazar said the pipeline could be built safely, with the right conditions.
White House refuted comments from former Energy Secretary Chu.
Hoeven said there are nearly enough votes for legislation that would set a hard deadline.