The pipeline developer said Keystone would be closely monitored.
Energy experts say the real problem for the U.S. isn’t a slow approval process.
It's the second letter sent to Obama within a month calling for immediate approval of the project.
Senate's 45 Republicans say it's time for a decision by the president.
Kerry will discuss energy and climate change issues with the two officials on Friday.
Sen. Hoeven said more pipelines are needed to help with the growing crude oil boom.
"I remain very confident" the pipeline will be approved, CEO Russ Girling said.
"If we need to bridge with rail, we will bridge," TransCanada's CEO said.
Officials believe the pipeline will be approved, if not by Obama, then by his successor.
The two Dems are concerned there was a conflict of interest in the State Dept.’s analysis.
The groups want Obama to reject Keystone XL in his State of the Union speech.
The groups say the oil flows are a "painful example" of Obama's energy policy.
Sen. Landrieu and others met with top Canadian officials to push approval of the pipeline.
"I am confident that in due course the project will ... proceed," Harper said.
The Northern Gateway Pipeline would help deliver crude from Canada to China.
The southern leg will begin delivering oil to Gulf Coast refineries in January.