In the Monday night episode of The Colbert Report, the joke was on Canada's oil industry.

That's because the featured guest appeared to take a dig at the industry's long-awaited, long-delayed Keystone XL pipeline project.

Unfortunately for project proponents, it just so happened that this skeptical guest was the man who controls its fate: U.S. President Barack Obama.

The issue was raised by pretend news anchor Stephen Colbert. The instant he began touting the potential merits of the plan, the show's young, left-leaning studio audience began booing.

"Obviously these young people weren't polled," Obama said.

The segment was taped at George Washington University in the U.S. capital, where the students left no doubt about their preference and the president didn't appear keen to dissuade them.

Obama went on to list the project's pros and cons. He dwelled far more heavily on the negative, continuing a recent pattern in which he's sounded dismissive of Keystone.

He might have to make a decision as early as next month.

Obama assured the audience that he'll be guided by climate-change considerations because the economic merit is too negligible to be the deciding factor.

"These young people are going to have to live in a world where we already know temperatures are going up," Obama said, referring again to the crowd.

"Keystone is a potential contributor of that ... We have to weigh that against the amount of jobs it's actually going to create — which are not a lot."

Obama said the pipeline wouldn't drive down gas prices for Americans, and experts generally agree with that. But he repeated a far more contested claim, that the pipeline would simply allow Canada to export its oil. He said the pipeline might be good for Canada but would only create a couple of thousand temporary construction jobs for Americans.

There were big cheers for what Obama said next: "We've got to measure that (benefit) against whether or not it's going to contribute to an overall warming of the planet — which could be disastrous."

The reaction of the audience illustrated the political dilemma for the president: Even if a majority of Americans support Keystone, there's deep opposition to it from the young, energetic base and donor class within the Democratic party, who want him to take a stand against it as part of his legacy on climate change.

And of all the things that might send a chill through the oil patch from what Obama said, it's this: the president appeared to be ignoring parts of his own administration's review that supported the project.

A State Department study this year concluded that the pipeline wouldn't increase greenhouse gases, nor would it be used to export Canadian crude.

The Canadian government has clung to those facts while arguing its pro-pipeline case. But there was the president again Monday night, talking about greenhouse gases and exports.

If it's any consolation to Canadian oil, he was far more dismissive of another project Colbert endorsed. The faux-anchor suggested building a pipeline to send Mexican migrants to Canada, which would then be too polite to turn them back.

"That sounds like a ridiculous idea," Obama retorted.

"But that's why you're where you are, and why I'm where I am."

The president's main reason for appearing on the show was to urge young, healthy people to sign up for insurance coverage, which would keep down premiums under his signature health plan.

Obama made that pitch while sitting in Colbert's chair for a segment.

As for Keystone, he could be making a decision soon.

He'll either be presented with a bill from the new, Republican-dominated Congress — which he would then sign or veto. Otherwise, he'd have to choose whether to approve the Alberta-to-Texas pipeline through the more customary process, following a review by his administration.