The White House still isn't saying whether it will approve or reject a permit for the northern segment of the Keystone XL pipeline, which would transport heavy crude oil from Canada to the United States. But the president's former national security adviser Thomas E. Donilon, told an Aspen Institute audience Tuesday that he "probably would" back it on energy security grounds.

In the last couple of minutes of his discussion with Walter Isaacson, the Aspen Institute's president and CEO, Donilon explained that the fact that U.S. energy production had increased in recent years made it easier for the administration to impose trade sanctions on Iran. Isaacson followed up by asking, "I know you’re not in the administration so maybe you could answer this would you recommend for the Keystone pipeline if you were there, for that reason?"

At first, Donilon, who is now a distinguished fellow of the Council on Foreign Relations, appeared uncomfortable at the prospect of voicing an opinion.

"It is hard to go from being an administration spokesperson to uh..." he said, prompting Isaacson to crack a joke.

"You want to turn off the microphone and just whisper it to us?" he asked.

After a little throat clearing, Donilon replied, "I probably would."

While Donilon's answer is not entirely surprising--many government officials privately back the project on the grounds that it would expand the oil supply the U.S. would receive from a trusted ally, as well as bolster our relationship with Canada more broadly--it does shed light on how some people within the administration view the issue. Equally important, Donilon has spoken during his time at the White House about the importance of addressing climate change, so this is not a comment coming from someone who is indifferent about the issue of global warming.

In April, for example, Donilon spoke about energy policy at the launch of Columbia University’s Center on Global Energy Policy," saying that in light of increased drought and rising sea levels across the globe, "This underscores the need – for the sake of our national security -- to reduce the greenhouse gas emissions that drive climate change and to ensure that we are as prepared as possible for the impacts of climate change."

Many environmental activists--including several influential backers of President Obama--oppose the pipeline on the grounds that it poses serious environmental risks and will accelerate climate change by making it easier to extract one of the world's most carbon-intense forms of fossil fuels.